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- We studied cortical amyloid – episodic memory association in twin pairs - Cognitively discordant twin pairs were identified using telephone interview - 45 twin pairs participated in PET imaging and in-person neuropsychological testing - Within-twin pair differences in amyloid and memory were associated with each other - Higher amyloid is related to poorer memory even when controlling for genetic effects We studied the association between episodic memory and cortical fibrillar β-amyloid pathology within twin pairs. Using telephone-administered cognitive screening of 1415 twin pairs in a population-based older Finnish Twin Cohort study, we identified 45 (mean [SD] age 72.9 [4.0] years, 40% women) cognitively discordant same-sex twin pairs (24 dizygotic and 21 monozygotic) without neurological or psychiatric disorders other than AD or mild cognitive impairment. In-person neuropsychological testing was conducted. Cortical amyloid was measured with carbon 11-labelled Pittsburgh compound B ([11C]PiB) positron emission tomography imaging and quantified as the average standardized uptake value ratio in cortical regions affected in AD. Larger within-twin pair differences in verbal immediate (r = -0.42) and delayed free recall (r = -0.41), and visual delayed free recall (r = -0.46) were associated with larger within-twin pair differences in [11C]PiB uptake (p 's < 0.01). Correlations were not significantly different in dizygotic and monozygotic pairs suggesting that the episodic memory-cortical amyloid relationship is not confounded by genetic effects. However, larger samples are needed to draw more definitive conclusions. [ABSTRACT FROM AUTHOR]

Objective: Binge eating disorder (BED) is a clinical eating disorder that is strongly and bidirectionally related to overweight and obesity. Little is known about how subclinical features of BED relate to weight development in adolescence and young adulthood.Method: Women (n = 2825) and men (n = 2423) from the community-based longitudinal FinnTwin16 cohort participated. Seven eating-related cognitions and behaviors similar to the defining features of BED were extracted from the Eating Disorder Inventory-2 and were assessed at a mean age of 24. We used linear mixed models to assess the association of features of BED with BMI trajectories across four waves of data collection (mean ages 16, 17, 18, and 24).Results: The number of features of BED at wave 4 (age 24) was significantly associated with BMI from age 16 years onwards. Those reporting more features of BED had gained more weight throughout adolescence and into their twenties.Conclusions: Features of BED in young adulthood were preceded by steeper BMI trajectories in adolescence. A higher number of features were consistently associated with higher BMI and more weight gain. [ABSTRACT FROM AUTHOR]

Background: Developmental relationships between tobacco use and suicide-related behaviors (SRB) remain unclear. Our objective was to investigate the longitudinal associations of tobacco use in adolescence and SRB in adulthood.Methods: Using a prospective design, we examined whether tobacco use in adolescence is associated with SRB (intentional self-injury, suicide ideation) in young adulthood in a population-based sample of 1330 twins (626 males, 704 females). The baseline and follow-up data were collected by professionally administered semi-structured poly-diagnostic interviews at ages 14 and 22, respectively.Results: After adjusting for multiple potential confounders, those who reported early-onset of regular tobacco use had a significantly increased risk for intentional self-injury, such as cutting or burning, at age 22 (adjusted odds ratio [AOR] 4.57, 95% CI 1.93-10.8) in comparison to those who had not at all initiated tobacco use. Also, daily cigarette smoking at baseline was associated with future intentional self-injury (AOR 4.45, 95% CI 2.04-9.70). Early-onset tobacco use was associated with suicidal ideation in females (AOR 3.69, 95% CI 1.56-8.72) but not in males. Considering any SRB, baseline daily smokers (AOR 2.13, 95% CI 1.12-4.07) and females with early onset of regular tobacco use (AOR 3.97, 95% CI 1.73-9.13) had an increased likelihood. Within-family analyses among twin pairs discordant for exposure and outcome controlling for familial confounds showed similar, albeit statistically non-significant, associations.Conclusion: Early-onset tobacco use in adolescence is longitudinally associated with SRB (intentional self-injury and/or suicide ideation) in young adulthood, particularly among females. Further investigation may reveal whether this association has implications for prevention of SRB in adolescence and young adulthood. [ABSTRACT FROM AUTHOR]

Summary: Robust sex differences in some spatial abilities that favor males have raised the question of whether testosterone contributes to those differences. There is some evidence for prenatal organizational effects of testosterone on male-favoring spatial abilities, but not much is known about the role of pubertal testosterone levels on adult cognitive abilities. We studied the association between pubertal testosterone (at age 14) and cognitive performance in young adulthood (at age 21–23), assessing male-favoring, female-favoring, and sex-neutral cognitive domains in a population-based sample of 130 male and 178 female twins. Pubertal testosterone was negatively associated with performance in the Mental Rotation Test in young adult men (r =−.27), while among women no significant associations between testosterone and cognitive measures were detected. The significant association among men remained after controlling for pubertal development. Confirmatory within-family comparisons with one-sided significance testing yielded a negative correlation between twin pair differences in testosterone levels and Mental Rotation Test performances in 35 male twin pairs (r =−.32): the twin brother with higher testosterone performed less well on the Mental Rotation Test. That association was evident in 18 pairs of dizygotic male twin pairs (r =−.42; analysis controlling for shared environmental effects). In contrast, the association of differences was not evident among 17 monozygotic male twin pairs (r =−.07; analysis controlling for shared genetic influences). Results suggest that pubertal testosterone levels are related specifically to male-favoring spatial ability and only among men. Within-family analyses implicated possible shared genetic effects between pubertal testosterone and mental rotation ability. [Copyright &y& Elsevier]

Abstract: Background: Obesity is related to an increased risk of several forms of cancer. However, findings from studies on haematological malignancies are inconsistent. Methods: We used prospectively collected data from two Swedish twin cohorts and the Finnish Twin Cohort (in total 70,067 persons) to study the effects of overweight and obesity on the development of leukaemia, non-Hodgkin lymphoma, Hodgkin’s lymphoma and myeloma. The cohorts were followed from baseline through 2002 (Sweden) and through 2004 (Finland). Results: We found a risk increase of myeloma with a relative risk (RR) of 2.1 (95% confidence interval [CI] 1.1–3.7) among obese persons, a RR of 2.5 (1.0–6.2) for chronic myeloid leukaemia and a RR of 2.7 (0.8–9.6) for acute lymphoblastic leukaemia among overweight persons as compared to normal-weighted ones. Conclusions: Our results add further evidence suggesting that overweight and obesity may have an impact on some haematological malignancies, in particular myeloma. [Copyright &y& Elsevier]

Abstract: We studied whether factors related to type of sport participated in as young adults and level of and changes in physical activity later in life predict changes in mood as well as functioning during a 6-year follow-up. A cohort of male Finnish former athletes (N =504), referents (N =349) was followed up for changes in physical activity, in relation to subsequent self-reported mood and functioning of daily living in 1985, 1995, and 2001. The mean age of the cohort was 68.6 years in 2001. Multinomial logistic regression analysis was used to assess changes in mood and functioning between 1995 and 2001 in relation to baseline values and changes in exposure variables and covariates. A low level of physical activity in 1985 predicted a decrease in physical functioning between 1995 and 2001 in the lowest physical activity compared to the highest quintile as well as poor physical functioning at the end of follow-up in 2001. An increase in physical activity between 1985 and 1995 protected against onset of anxiety between 1995 and 2001. Physical activity for elderly seems to have an important role in reducing the progress of deficiencies in physical functioning and in preventing onset of anxiety. [Copyright &y& Elsevier]

Adolescent mental health problems impose a significant burden. Exploring evolving social environments could enhance comprehension of their impact on mental health. We aimed to depict the trajectories of the neighborhood social exposome from middle to late adolescence and assess the intricate relationship between them and late adolescent mental health. Participants (n = 3965) from the FinnTwin12 cohort with completed questionnaires at age 17 were used. Nine mental health measures were assessed. The social exposome comprised 28 neighborhood social indicators. Trajectories of these indicators from ages 12 to 17 were summarized via latent growth curve modeling into growth factors, including baseline intercept. Mixture effects of all growth factors were assessed through quantile-based g-computation. Repeated generalized linear regressions identified significant growth factors. Sex stratification was performed. The linear-quadratic model was the most optimal trajectory model. No mixture effect was detected. Regression models showed some growth factors saliently linked to the p-factor, internalizing problems, anxiety, hyperactivity, and aggression. The majority of them were baseline intercepts. Quadratic growth factors about mother tongues correlated with anxiety among sex-combined participants and males. The linear growth factor in the proportion of households of couples without children was associated with internalizing problems in females. We were limited to including only neighborhood-level social exposures, and the multilevel contextual exposome situation interfered with our assessment. Trajectories of the social neighborhood exposome modestly influenced late adolescent mental health. Tackling root causes of social inequalities through targeted programs for living conditions could improve adolescent mental health. • Trajectories of the neighborhood social exposome were depicted in adolescence. • No mixture effect of trajectories on adolescent mental health was found. • Most of the growth factors selected by regression models were baseline intercepts. • Changes in neighborhood language and household structures linked with mental health. • Results may be affected by the multilevel contextual exposome situation. [ABSTRACT FROM AUTHOR]

Although the relationship of alcohol use with mortality has been extensively studied, these epidemiological studies are mainly based on single assessments of alcohol use and do not differentiate between causal and non-causal explanations. With four decades of follow-up in the older Finnish Twin Cohort, we examined the relationship of mortality with patterns of alcohol use in a genetically informative sample of MZ and DZ pairs. Three questionnaire surveys of the Finnish Twin Cohort of like-sex twin pairs born 1930–1957 were conducted in 1975, 1981 & 1990. Alcohol consumption was assessed in an identical fashion in all surveys as the use of beer, wine and spirits. These were converted to the number of standard drinks consumed on average. Based on responses to all three surveys from 11,382 men and women, we first analysed the average consumption, ranging from abstinence over all 15 years (29% of all) to an average of 28 or more drinks per week (2%). Next, 3,656 persons whose consumption level (abstinent, one drink per week, 2–6, 7–13 or 14 or more drinks weekly) was the same across all time points were studied. Total mortality was obtained for response date in 1990 to end of follow-up 12/31/2016 with 1,977 deaths. Individual and within pair analyses were conducted using Cox proportional hazards regression models to derive hazard ratios (HR) for death. In analyses of all individuals, the lowest age-sex adjusted mortality was found for those drinking 1 drink per week on average, while consistent abstainers (HR 1.27,95%CI 1.09 to 1.49) and those consuming more had significantly elevated risks. The HR for 14 to 20 drinks weekly was 2.95, 21 to 27 drinks/wk had an HR of 4.42 while consuming 28 or more drinks/wk on average between 1975 and 1990 had an HR of 5.42 (95%CI 4.14to 7.10). For those with stable drinking patterns (n=3,656 twins, 648 deaths) the pattern was similar: those consistently drinking just one drink weekly had the lowest mortality, HR elevated to 1.49 for consistent abstainers; those drinking 2–6 drinks weekly had an HR of 1.43, 7 to 13 drinks an HR of 3.23, and those drinking at least 14 drinks at all three surveys an HR of 4.91. Within-family analyses found a pattern of mortality similar to the individual-based analyses, with an HR of 6.38 (3.14 to 13.0) for those twins consuming, on average, 28 or more drinks weekly in the prior 15 years compared to their co-twins drinking one drink weekly on average, with estimates for intermediate amounts lying between the two extremes. Our within-pair analyses were consistent with the individual analyses, with increased risks at the high end of use, but with a significant increase in mortality already at levels considered by many to represent safe drinking (i.e. 7 to 13 drinks weekly). Interestingly the results were similar and significant in both MZ and DZ pairs. The increased mortality associated with alcohol use is not due to genetic or other influences shared by co-twins but compatible with a causal effect. [ABSTRACT FROM AUTHOR]

This paper examines the links between risky health behaviors and labor market success. We provide new evidence on the joint relationships between the most prominent forms of risky health behavior − alcohol consumption, smoking and physical inactivity − and long-term labor market outcomes. We use twin data for Finnish men and women linked to register-based individual information on earnings and labor market attachment. The twin data allow us to account for shared family and environmental factors and to measure risky health behaviors in 1975 and 1981. The long-term labor market outcomes were measured in adulthood as an average over the period 1990–2009. The sample sizes are 2156 and 2498 twins, for men and women, respectively. We find that being both a smoker and a heavy drinker in early adulthood is negatively related to long-term earnings and employment later in life, especially for men. We conclude that how and why risky health behaviors cluster and how that affects individual level outcomes call for more attention. [ABSTRACT FROM AUTHOR]

Background: We assessed whether the Eating Disorder Inventory (EDI) is suitable for screening binge eating disorder (BED) in young women.Method: Young women (N=2825) from the 1975-79 birth cohorts of Finnish twins were assessed by questionnaires, including subscales of the EDI. For a subset of women (N=548), we established DSM-5 diagnoses of BED; 16 women had lifetime BED. We compared screening properties of the EDI scales using receiver operating characteristic (ROC) analysis, determined optimal cutoff points, and calculated sensitivities and specificities.Results: The best screen for DSM-5 BED was the global score of three subscales (Bulimia, Drive for Thinness, Body Dissatisfaction) with an area under the curve (AUC) of 0.86. Its sensitivity was 87% and specificity 76% at cutoff ≥21. Three individual subscales had acceptable screening properties: Bulimia (AUC 0.83; sensitivity 80%, specificity 78% at cutoff ≥2), Drive For Thinness (AUC 0.82; sensitivity 87%, specificity 72% at cutoff ≥7), and Body Dissatisfaction (AUC 0.81; sensitivity 93%, specificity 60% at cutoff ≥8).Conclusion: The EDI performed well as a screening tool for BED in our community-based sample of young twin women. Future studies should assess its value in other populations and in clinical settings. [ABSTRACT FROM AUTHOR]

The understanding of the molecular genetic contributions to smoking is largely limited to the additive effects of individual single nucleotide polymorphisms (SNPs), but the underlying genetic risk is likely to also include dominance, epistatic, and gene-environment interactions. To begin to address this complexity, we attempted to identify genetic interactions between rs16969968, the most replicated SNP associated with smoking quantity, and all SNPs and genes across the genome. Using the UK Biobank European subsample, we found one SNP, rs1892967, and two genes, PCNA and TMEM230 , that showed a significant genome-wide interaction with rs16969968 for log10 CPD and raw CPD, respectively, in a sample of 116 442 individuals who self-reported currently or previously smoking. We extended these analyses to individuals of South Asian descent and meta-analyzed the combined sample of 117 212 individuals of European and South Asian ancestry. We replicated the gene findings in a meta-analysis of five Finnish samples (N=40 140): FinHealth, FINRISK, Finnish Twin Cohort, GeneRISK, and Health-2000–2011. To our knowledge, this represents the first reliable epistatic association between single nucleotide polymorphisms for smoking behaviors and provides a novel direction for possible future functional studies related to this interaction. Furthermore, this work demonstrates the feasibility of these analyses by pooling multiple datasets across various ancestries, which may be applied to other top SNPs for smoking and/or other phenotypes. • We explored interactions between rs16969968 and all SNPs and genes genome-wide. • One SNP, rs1892967, and two genes, PCNA and TMEM230 , significantly interacted with rs16969968 for smoking quantity. • We replicated the gene findings in a meta-analysis of five Finnish samples comprising over 40, 000 individuals. • This is the first reliable epistatic association between single nucleotide polymorphisms for smoking behaviors. [ABSTRACT FROM AUTHOR]

• Obesity matrisome include 130 signature genes in adipose tissue and 71 in adipocytes. • Adipocyte obesity matrisome show hypertrophic inflammatory phenotype. • Adipose tissue obesity matrisome shows remodeling phenotype. • Novel metabolism-linked matrisome genes are CTSA, CSTO, FAM20B and NGLY1. Adipose tissue is a central regulator of metabolic health and its failure in obesity is a major cause of weight associated comorbidities, such as type 2 diabetes. Many extracellular matrix proteins, represented by matrisome, play a critical role in balancing adipose tissue health and dysfunction. Extracellular matrix components, produced by different cell types of adipose tissue, can modulate adipocyte function, tissue remodeling during expansion, angiogenesis, and inflammation and also form fibrotic lesions in the tissue. In this study, we investigated changes in matrisome of whole adipose tissue and adipocytes in human obesity. We investigated further the networks and biological pathways of the genes related to the changes and their association to development of metabolic dysfunction linked to type 2 diabetes. We used transcriptome data and clinical metabolic parameters from a rare weight-discordant MZ twin cohort. The Heavy-Lean differential matrisome gene expression (Δmatrisome) and differential metabolic parameters reflect changes in adipose tissue upon weight gain and changes in whole body glucose, insulin metabolism, as well as lipid status. We report that obesity Δmatrisome shows high specificity with 130 and 71 of the 1068 matrisome genes showing altered expression in the adipose tissue and adipocytes of heavier co-twin, respectively. The Δmatrisome differs considerably between adipose tissue vs adipocytes which reflects inflammation of hypertrophic adipocytes and the remodeling activity of the rest of the tissue resident cells. The obesity Δmatrisome is discussed extensively in the light of existing evidence and novel significant associations to obesity are reported to matrisome genes; cathepsin A, cathepsin O, FAM20B and N-glycanase1. [ABSTRACT FROM AUTHOR]

The impact of diet on the gut microbiota has usually been assessed by subjecting people to the same controlled diet and thereafter following the shifts in the microbiota. In the present study, we used habitual dietary intake, clinical data, quantitative polymerase chain reaction, and denaturing gradient gel electrophoresis (DGGE) to characterize the stool microbiota of Finnish monozygotic twins. The effect of diet on the numbers of bacteria was described through a hierarchical linear mixed model that included the twin individuals, stratified by body mass index, and their families as random effects. The abundance and diversity of the bacterial groups studied did not differ between normal-weight, overweight, and obese individuals with the techniques used. Intakes of energy, monounsaturated fatty acids, n3 polyunsaturated fatty acids (PUFAs), n6 PUFAs, and soluble fiber had significant associations with the stool bacterial numbers (e.g., increased energy intake was associated with reduced numbers of Bacteroides spp.). In addition, co-twins with identical energy intake had more similar numbers and DGGE-profile diversities of Bacteroides spp. than did the co-twins with different intake. Moreover, the co-twins who ingested the same amounts of saturated fatty acids had very similar DGGE profiles of Bacteroides spp., whereas the co-twins with similar consumption of fiber had a very low bifidobacterial DGGE-profile similarity. In conclusion, our findings confirm that the diet plays an important role in the modulation of the stool microbiota, in particular Bacteroides spp. and bifidobacteria. [ABSTRACT FROM AUTHOR]

Abstract: Although potential environmental influences on hedonic responses to oral pungency have been identified, little is known of the possible role of genetics underlying these responses. We explored the contribution of genetic and environmental influences on the pleasantness of oral pungency and spicy foods. Respondents were young adult Finnish twins (n=331, 21–25years), including 47 complete monozygotic and 93 dizygotic twin pairs and 51 twin individuals without their co-twin. Pleasantness and intensity of strawberry jelly spiked with capsaicin (0.0001% w/v) relative to untainted strawberry jelly were rated. Furthermore, pleasantness of spicy foods and oral pungency caused by spices were rated based on food names in a questionnaire. Respondents were grouped as non-likers, medium-likers, and likers by their pleasantness responses to capsaicin spiked jelly. The contribution of genetic and environmental factors to variation and co-variation of the pleasantness traits was analyzed using quantitative genetic modeling. The non-likers perceived oral pungency as more intense (sensory) and rated pleasantness of spicy foods and pungent sensations caused by spices (questionnaire) as less pleasant than the likers. Genetic factors accounted for 18–58% of the variation in the pleasantness of oral pungency, spicy foods and pungent sensations. The rest was due to environmental factors. All pleasantness traits (sensory and questionnaire based) were shown to share a common genetic variance. This indicates that an underlying genetic aptitude to like oral pungency, and spicy foods exists and it is expressed in these measures. The findings broaden the understanding of the diverse nature of individual food preferences and motivate further search for the underlying genetic components of oral pungency. [Copyright &y& Elsevier]

Abstract: Background context: There are differing views as to the causes of disc degeneration. One view, referred to as a cumulative or repetitive injury model, explains disc degeneration, in great part, as the result of “wear and tear” on the disc from routine daily exposures to physical loading or biomechanical forces. Perhaps paradoxically, such physical loading has been thought to be generally beneficial for other structures of the musculoskeletal system. Purpose: The goal of this study was to investigate the associations of physical loading from body weight using quantitative measures of disc degeneration. Study design: This is an exposure-discordant twin study. Methods: We selected 44 pairs of healthy male monozygotic (MZ) twins with 8 kg or more discordance in body weight (mean 13 kg), with lumbar magnetic resonance imaging and bone density measurements available. The main outcome of disc degeneration was assessed through quantitatively measured disc height, and disc signal intensity and signal variation adjusted by the intrabody reference, adjacent cerebrospinal fluid signal, at L1–L4. Data on suspected constitutional and environmental risk factors were available for control of possible confounding factors. Results: Higher body weight was associated with 6.2% higher bone density in the lumbar spine, confirming an effective discordance (p<.0001). Disc signal variation was 5.4% higher (“better”) among the heavier MZ co-twins (p=.005), but the 2.6% higher disc heights and 2.9% higher adjusted disc signals were not statistically significant. Conclusions: Contrary to common beliefs, our findings suggest that cumulative or repetitive loading because of higher body mass (nearly 30 pounds on average) was not harmful to the discs. In fact, a slight delay in L1–L4 disc desiccation was observed in the heavier men, as compared with their lighter twin brothers. [Copyright &y& Elsevier]

Abstract: Background: While temperamental characteristics have been related to the onset of cannabis use, it is not clear at what point(s) along the trajectory from early onset of tobacco use (EOT) to early onset of cannabis use (EOC) these characteristics exert their impact. This study examined if (1) temperamental characteristics predispose to EOT that on its turn predisposes to EOC, and (2) temperament moderates the importance of EOT on the progression to EOC. Methods: Data from 1848 (83%) participants in the TRacking Adolescents’ Individual Lives Survey (TRAILS), a prospective population study of Dutch adolescents, were analyzed. We used parent-reports on the Early Adolescent Temperament Questionnaire to assess the dimensions of high-intensity pleasure, frustration, effortful control, shyness and fearfulness at age 10–12. EOT and EOC were defined as use at least once before the ages of 12 and 13 years, respectively, assessed by means of self-reports. We performed mediation and moderation analyses in Mplus. Results: High levels of high-intensity pleasure predisposed to entrance in the trajectory from EOT to EOC. Once tobacco use had been initiated at early age, low levels of shyness and high levels of high-intensity pleasure increased the risk of progression to EOC. Conclusions: Besides a common liability for EOT and EOC based on temperament, the risk of transition from tobacco to cannabis use is modified by temperamental characteristics. Differences in interplay with other risk factors may explain the impact of temperament on distinct points along the substance use trajectory. [Copyright &y& Elsevier]

Abstract: Background context: Disc degeneration was commonly viewed over much of the last century as a result of aging and “wear and tear” from mechanical insults and injuries. Thus, prevention strategies and research in lumbar degenerative changes and associated clinical conditions focused largely on mechanical factors as primary causes using an “injury model.” The Twin Spine Study, a research program on the etiology and pathogenesis of disc degeneration, has contributed to a substantial revision of this view of determinants of lumbar disc degeneration. Purpose: To provide a review of the methods and findings of the Twin Spine Study project. Study design/setting: Narrative review of the Twin Spine Study. Methods: The Twin Spine Study, which started in 1991, is a multidisciplinary, multinational research project with collaborators primarily in Canada, Finland, and the United States. The most significant investigations related to determinants of disc degeneration included occupational exposures, driving and whole-body vibration exposure, smoking exposure, anthropomorphic factors, heritability, and the identification of genotypes associated with disc degeneration. Results: Among the most significant findings were a substantial influence of heredity on lumbar disc degeneration and the identification of the first gene forms associated with disc degeneration. Conversely, despite extraordinary discordance between twin siblings in occupational and leisure-time physical loading conditions throughout adulthood, surprisingly little effect on disc degeneration was observed. Studies on the effects of smoking on twins with large discordance in smoking exposure demonstrated an increase in disc degeneration associated with smoking, but this effect was small. No evidence was found to suggest that exposure to whole-body vibration through motorized vehicles leads to accelerated disc degeneration in these well-controlled studies. More recent results indicate that the effect of anthropometric factors, such as body weight and muscle strength on disc degeneration, although modest, appear in this work to be greater than those of occupational physical demands. In fact, some indications were found that routine loading may actually have some benefits to the disc. Conclusions: The once commonly held view that disc degeneration is primarily a result of aging and “wear and tear” from mechanical insults and injuries was not supported by this series of studies. Instead, disc degeneration appears to be determined in great part by genetic influences. Although environmental factors also play a role, it is not primarily through routine physical loading exposures (eg, heavy vs. light physical demands) as once suspected. [Copyright &y& Elsevier]

Abstract: Background context: Disc degeneration was commonly viewed over much of the last century as a result of aging and “wear and tear” from mechanical insults and injuries. Thus, prevention strategies and research in lumbar degenerative changes and associated clinical conditions focused largely on mechanical factors as primary causes using an “injury model.” The Twin Spine Study, a research program on the etiology and pathogenesis of disc degeneration, has contributed to a substantial revision of this view of determinants of lumbar disc degeneration. Purpose: To provide a review of the methods and findings of the Twin Spine Study project. Study design/setting: Narrative review of the Twin Spine Study. Methods: The Twin Spine Study, which started in 1991, is a multidisciplinary, multinational research project with collaborators primarily in Canada, Finland, and the United States. The most significant investigations related to determinants of disc degeneration included occupational exposures, driving and whole-body vibration exposure, smoking exposure, anthropomorphic factors, heritability, and the identification of genotypes associated with disc degeneration. Results: Among the most significant findings were a substantial influence of heredity on lumbar disc degeneration and the identification of the first gene forms associated with disc degeneration. Conversely, despite extraordinary discordance between twin siblings in occupational and leisure-time physical loading conditions throughout adulthood, surprisingly little effect on disc degeneration was observed. Studies on the effects of smoking on twins with large discordance in smoking exposure demonstrated an increase in disc degeneration associated with smoking, but this effect was small. No evidence was found to suggest that exposure to whole-body vibration through motorized vehicles leads to accelerated disc degeneration in these well-controlled studies. More recent results indicate that the effect of anthropometric factors, such as body weight and muscle strength on disc degeneration, although modest, appear in this work to be greater than those of occupational physical demands. In fact, some indications were found that routine loading may actually have some benefits to the disc. Conclusions: The once commonly held view that disc degeneration is primarily a result of aging and “wear and tear” from mechanical insults and injuries was not supported by this series of studies. Instead, disc degeneration appears to be determined in great part by genetic influences. Although environmental factors also play a role, it is not primarily through routine physical loading exposures (eg, heavy vs. light physical demands) as once suspected. [Copyright &y& Elsevier]

Abstract: Background: We examined mid-adolescent psychosocial problems as risk factors for subsequent depression up to adulthood proper, and differences in these for episodic and persistent depression. Methods: In a 16-year follow-up of an urban Finnish community cohort (547 males and 714 females) from age 16 years risk factors for subsequent depression (S-BDI) were studied. Data were collected with a classroom questionnaire at 16 years and a postal questionnaire at 22 and 32 years. Differences in predictors for episodic depression (only at age of 22 or 32 y) and persistent depression (both at 22 and 32 y) were studied using logistic and multinomial regression analyses. Results: Mid-adolescent depressive symptoms predicted persistent and female sex episodic depression. Low self-esteem, dissatisfaction with academic achievement, problems with the law, having no dating experiences, and parental divorce all predicted both episodic and persistent depression. Limitations: We had two assessment points in adulthood, but no information about depression between these. Conclusions: The associations between mid-adolescent psychosocial problems and subsequent depression extended up to adulthood proper, somewhat differently for episodic and persistent depression. Preventive efforts should be focused towards young people at risk. [Copyright &y& Elsevier]

The present study describes PET, MRI, and neuropsychological findings in 90-year-old monozygotic female twins, who have remained discordant for probable Alzheimer’s disease (AD) for at least 7 years. These findings were compared with those of healthy persons composing the reference group (seven women, three men; the mean±S.D. age: 73.3±3.3 years). Twins’ life histories were remarkably similar, except for continuous NSAID use of the unaffected twin for decades. The regional cerebral glucose metabolic rates (rCMRgluc) and all but two CERAD test scores of the affected twin were more than 2 S.D. below the mean values of the reference group. These values were normal in the unaffected twin. The affected twin had moderate hippocampal and temporoparietal atrophy, whereas the hippocampi were intact, and cortical atrophy was mild in the unaffected twin. These findings indicate that the twins were discordant for AD, even though they had reached the age in which the prevalence of AD is high among women. Our results further address the influence of environmental factors on the onset of AD, especially the possible protective effect of anti-inflammatory medication. [Copyright &y& Elsevier]

Subclinical psychosis, including schizotypal indicators and psychotic experiences, predicts future suicidal ideation. This relationship may reflect unmeasured confounding from environmental factors, genetic factors, or both. We used a genetically-informative twin design to understand if the association between subclinical psychosis and suicidal ideation is independent of shared genetic and environmental factors. We analysed cross-sectional associations of age-22 self-reported subclinical psychosis (positive, negative, and disorganised features) with suicidal ideation in twins participating in the FinnTwin12 study (maximum n = 1213). Then, we analysed the reverse association of age-14 suicidal ideation with age-22 subclinical psychosis. Associations were studied first among individuals and then within monozygotic (MZ) and dizygotic (DZ) pairs. Individual-level analyses showed that all subclinical psychosis factors were associated with suicidal ideation. In within-pair analyses, estimates of associations were lower for MZ pairs than DZ pairs, except for the negative schizotypy-suicidal ideation association where estimates were consistent across individual-level and within-pair analyses. Findings provide evidence that the association between negative features and suicide ideation is not explained by familial factors and may be causal, though the possibility of confounding by individual-specific environmental factors and reverse causation cannot be ruled out. The relationships of positive and disorganised subclinical psychosis features with suicidal ideation cannot be explained by confounding due to environmental factors shared between siblings, but their associations may be due to shared genetic factors. [ABSTRACT FROM AUTHOR]

• The moderate-strength association between PA and cognition or reduced dementia incidence may be explained in part by familial factors. • In MZ co-twin control design, PA may increase GM volume in striatal, prefrontal and hippocampal regions independent of familial factors. • In MZ co-twin control design, LTPA may expedite preconcious visual processing and dampen strength of unattended deviant somatosensory stimuli. Regular physical activity (PA) offers positive effects on the human body. However, the effects of PA on cognition and in the brain are less clear. In this paper, we narratively review the relationship of PA with cognition and dementia, first from general perspective and then through genetically informed studies on the topic. Then we move on to imaging studies on exercise and brain anatomy first by presenting an overall picture of the topic and then discussing brain imaging studies addressing PA and brain structure in twins in more detailed way. Regarding PA and cognition or dementia, genetically informed studies are uncommon, even though the relationship between PA and cognitive ageing has been extensively studied. It is challenging to find twin pairs discordant for PA and dementia. Concerning brain imaging studies, among PA discordant young adult twin pairs, the more active co-twins showed larger gray matter volumes in striatal, prefrontal, and hippocampal regions and in electrophysiological studies automatic deviance-detection processes differed in brain regions involved with sensorimotor, visual and memory functions. [ABSTRACT FROM AUTHOR]

Background: Longitudinal studies enhance understanding of the complex reciprocal relationship between smoking and depression from adolescence to young adulthood. Examining bi-directional associations between cigarette smoking and depressive symptoms in a genetically informative twin design can help to understand whether the associations are independent of shared genetic and environmental factors.Methods: We analyzed longitudinal data on smoking and depressive symptoms in twins participating in the adolescent (mean age 17.5) and young adult (mean age 21.9) surveys of the FinnTwin12 study (maximum N = 2,954 individuals; 1,154 twin pairs). At both waves, self-reported depressive symptoms, assessed with the 10-item version of the General Behavior Inventory (GBI), and smoking status were analyzed. The bi-directional associations were first studied among individuals and then within monozygotic and dizygotic twin pairs.Results: When adjusted for multiple covariates and baseline depressive symptoms, daily smokers at age 17 had higher depressive symptom scores at age 22 than never smokers (Incidence Rate Ratio = 1.17, 95% CI: 1.03-1.33). Similarly, when adjusted for covariates and baseline smoking, higher score in GBI at age 17 was associated with an increased likelihood of being a non-daily (Relative Risk Ratio (RRR) = 1.06, 95% CI: 1.01-1.11) or daily (RRR = 1.05, 95% CI: 1.00-1.10) smoker at age 22. No associations were found in within-pair analyses, suggesting that the individual-level association is explained by shared familial liabilities.Conclusion: During the developmental period from adolescence to adulthood, cigarette smoking and depressive symptoms are reciprocally associated. However, these associations are confounded by shared genetic and other familial liabilities. [ABSTRACT FROM AUTHOR]

Highlights • Heavier women had lower serum DHEA, DHT and SHBG compared to their leaner co-twins. • Serum DHEA concentration was best predicted by percent body fat within twin pairs. • Insulin resistance did not explain serum androgen or SHBG levels within twin pairs. • STS and AKR1C genes were more expressed in adipose tissue from the heavier women. • Intra-abdominal fat and leptin were important regarding adipocyte expression of STS. Abstract Objective Obesity may alter serum steroid concentrations and metabolism. We investigated this in healthy young women with increased body fat and their leaner co-twin sisters. Design Age and genetic background both strongly influence serum steroid levels and body composition. This is a cross-sectional study of 13 female monozygotic twin pairs (age, 23–36 years), ten of which were discordant for body mass index (median difference in body weight between the co-twins, 19 kg). Methods We determined body composition by dual energy X-ray absorptiometry and magnetic resonance imaging, serum androgens by liquid chromatography-tandem mass spectrometry, and mRNA expression of genes in subcutaneous adipose tissue and adipocytes. Results The heavier women had lower serum dehydroepiandrosterone (DHEA), dihydrotestosterone (DHT), and sex hormone-binding globulin (SHBG) (P < 0.05 for all) compared to their leaner co-twins with no differences in serum testosterone or androstenedione levels. Serum DHEA correlated inversely with %body fat (r = −0.905, P = 0.002), and DHT positively with SHBG (r = 0.842, P = 0.002). In adipose tissue or adipocytes, expressions of STS (steroid sulfatase) and androgen-related genes were significantly higher in the heavier compared to the leaner co-twin, and within pairs, correlated positively with adiposity but were not related to serum androgen levels. None of the serum androgen or SHBG levels correlated with indices of insulin resistance. Conclusions Serum DHEA levels were best predicted by %body fat, and serum DHT by SHBG. These or other serum androgen concentrations did not reflect differences in androgen-related genes in adipose tissue. General or intra-abdominal adiposity were not associated with increased androgenicity in young women. [ABSTRACT FROM AUTHOR]

Background and aims Studies report that both high and low total cholesterol (TC) elevates SAH risk. There are few prospective studies on high-density lipoproteins (HDL-C) and low-density lipoproteins (LDL-C), and apparently none concerns apolipoproteins A and B. We aimed to clarify the association between lipid profile and SAH risk. Methods The National FINRISK study provided risk-factor data recorded at enrolment between 1972 and 2007. During 1.52 million person-years of follow-up until 2014, 543 individuals suffered from incident hospitalized SAH or outside-hospital-fatal SAH. Cox proportional hazards model was used to calculate the hazard ratios and multiple imputation predicted ApoA1, ApoB, and LDL-C values for cohorts from a time before apolipoprotein-measurement methods were available. Results One SD elevation (1.28 mmol/l) in TC elevated SAH risk in men (hazard ratio (HR) 1.15 (95% CIs 1.00–1.32)). Low HDL-C levels increased SAH risk, as each SD decrease (0.37 mmol/l) in HDL-C raised the risk in women (HR 1.29 (95% CIs 1.07–1.55)) and men (HR 1.20 (95% CIs 1.14–1.27)). Each SD increase (0.29 g/l) in ApoA1 decreased SAH risk in women (HR 0.85 (95% CIs 0.74–0.97)) and men (HR 0.88 (95% CIs 0.76–1.02)). LDL-C (SD 1.07 mmol/l) and ApoB (SD 0.28 g/l) elevated SAH risk in men with HR 1.15 (95% CIs 1.01–1.31) and HR 1.26 (95% CIs 1.10–1.44) per one SD increase. Age did not change these findings. Conclusions An adverse lipid profile seems to elevate SAH risk similar to its effect in other cardiovascular diseases, especially in men. Whether SAH incidence diminishes with increasing statin use remains to be studied. [ABSTRACT FROM AUTHOR]

Objectives: To assess factors associated with successful weight maintenance over ten years in a prospective general population sample of young adults.Material and Methods: Our study comprised 2452 women and 2227 men born in 1975-1979 (mean age at baseline 24 years, attrition 27.1%). Weight maintenance was defined as weight maintained within ±5% of baseline body mass index (BMI). We examined the role of various sociodemographic and lifestyle factors in successful weight maintenance.Results: Relatively few young adults were able to maintain their weight over ten years (28.6% of women vs. 23.0% of men); net weight loss was uncommon (7.5% and 3.8%). Most participants gained weight (mean annual weight gain was 0.9 kg in women and 1.0 kg in men). Among women, exercise was associated with successful weight maintenance, but having two or more children, frequent use of sweet drinks, irregular eating, history of dieting (intentional weight loss) and low life satisfaction were associated with weight gain. Among men, higher baseline BMI and higher education were associated with successful weight maintenance, whereas irregular eating, history of dieting and smoking were associated with weight gain.Conclusions: Only about a quarter of young adults were able to resist weight gain. Regular eating and having no history of dieting were associated with successful weight maintenance in young women and men. [ABSTRACT FROM AUTHOR]

Responses to sweetness are reported in two populations, one segmented by gender and age, and the other one by gender only. The strength of the association between liking for specific sweet foods and liking for an aqueous sucrose solution (20% w/v) is also tested, and health attitudes examined. British adults (n = 1855, age 17–82, mean 55 years, 90% women) and Finnish young adults (n = 1292, age 20–25, mean 22 years, 54% women) rated their liking of ten sweet foods and beverages based on product names, and completed questionnaires on Craving for Sweet Foods (CSF) and General Health Interest (GHI). One-half of Brits and a third of Finns rated liking and intensity of sucrose solution. In factor analysis, identical categories of liking for sweet products were formed in each population, one consisting of five processed sweets (“Goodies”), and the other of naturally sweet fruits and berries (“Fruits”). Sugared and sugar-free s oft drinks and fruit juice loaded on the third factor. After age 50, British men scored higher than British women in CSF and liking for several sweet products; Finnish women scored higher than Finnish men in CSF and liking for most sweet products. GHI was positively associated with liking for Fruits and negatively with liking for sugared soft drinks. Sucrose solution was better liked by British men than women, with no gender difference in Finns. Liking for sucrose solution was only weakly associated with liking for sweet products based on product names. In two demographically different European populations, attraction to sweet gathered in similar product categories, but manifested differently at different ages and each gender. [ABSTRACT FROM AUTHOR]

Obesity and ageing are associated with lower serum testosterone levels in men. How fat distribution or adipose tissue metabolism, independent of genetic factors and age, are related to sex steroid metabolism is less clear. We studied the associations between adiposity and serum sex hormone concentrations, and mRNA expression of genes regulating sex hormone metabolism in adipose tissue in young adult male monozygotic (MZ) twin pairs. The subjects [n = 18 pairs; mean age, 32 years; individual body mass indexes (BMIs) 22–36 kg/m 2 ] included 9 male MZ twin pairs discordant for BMI [intra-pair difference (Δ) in BMI ≥3 kg/m 2 ]. Sex steroid concentrations were determined by liquid chromatography–tandem mass spectrometry, body composition by dual-energy X-ray absorptiometry and magnetic resonance imaging, and mRNA expressions from subcutaneous adipose tissue by Affymetrix. In BMI-discordant pairs (mean ΔBMI = 5.9 kg/m 2 ), serum dihydrotestosterone (DHT) was lower [mean 1.9 (SD 0.7) vs . 2.4 (1.0) nmol/l, P = 0.040] and mRNA expressions of DHT-inactivating AKR1C2 ( P = 0.021) and cortisol-producing HSD11B1 ( P = 0.008) higher in the heavier compared to the leaner co-twins. Serum free 17 β -estradiol (E2) was higher [2.3 (0.5) vs . 1.9 (0.5) pmol/l, P = 0.028], and in all twin pairs, serum E2 and estrone concentrations were higher in the heavier than in the leaner co-twins [107 (28) vs . 90 (22) pmol/l, P = 0.006; and 123 (43) vs . 105 (27) pmol/l, P = 0.025]. Within all twin pairs, i.e. independent of genetic effects and age, 1) the amount of subcutaneous fat inversely correlated with serum total and free testosterone, DHT, and sex hormone-binding globulin (SHBG) concentrations ( P < 0.01 for all), 2) intra-abdominal fat with total testosterone and SHBG ( P < 0.05), and 3) liver fat with SHBG ( P = 0.006). Also, 4) general and intra-abdominal adiposity correlated positively with mRNA expressions of AKR1C2 , HSD11B1 , and aromatase in adipose tissue ( P < 0.05). In conclusion, acquired adiposity was associated with decreased serum DHT and increased estrogen concentrations, independent of genetic factors and age. The reduction of DHT could be linked to its increased degradation (by AKR1C2 and HSD11B1) and increased estrogen levels to increased adiposity-related expression of aromatase in adipose tissue. [ABSTRACT FROM AUTHOR]

Background: Cigarette smoking and depression are major public health concerns, but longitudinal research on the association between smoking and antidepressant use is scarce. The purpose of this study was to investigate, whether smoking predicts antidepressant medication during a 10-year follow-up.Methods: A questionnaire was administered to Finnish adult twins in 1990. Antidepressant prescription data during 1995-2004 were obtained from the register of the Finnish Social Insurance Institution and linked to the survey data. Cox Proportional Hazard Models among 10,652 individuals (1075 cases, 9577 controls) assessed the risk for depression in the cohort, whereas within-pair comparisons of smoking twins with their non-smoking co-twins controlled for shared familial influences.Results: Daily smokers had a significantly elevated likelihood for having antidepressant prescriptions in the follow-up. Based on the analysis among those without baseline depression, heavy daily smokers had a significantly elevated likelihood (HR 1.56, 95% CI 1.17-2.08) for antidepressant prescription when adjusted for all confounders. Similar analysis using pairs discordant for antidepressant medication confirmed that daily smoking twins had a higher likelihood for prescriptions (HR 1.98, 95% CI 1.11-3.54) compared with their non-smoking co-twins. The estimates were for MZ pairs (HR 1.78, 95% CI 0.48-6.55) and DZ pairs (HR 1.92, 95% CI 0.99-3.72), respectively.Limitations: Changes in smoking status after baseline cannot be accounted for. Reversed association between depression and smoking cannot be ruled out.Conclusion: Daily smoking predicts antidepressant medication, even when controlling for essential confounders and familial factors. This study highlights the need of systematically assessing depressive symptoms among smokers. [ABSTRACT FROM AUTHOR]

The consequences of heavy alcohol use remain a serious public health problem. Consistent evidence has demonstrated that both genetic and social influences contribute to alcohol use. Research on gene-environment interaction (GxE) has also demonstrated that these social and genetic influences do not act independently. Instead, certain environmental contexts may limit or exacerbate an underlying genetic predisposition. However, much of the work on GxE and alcohol use has focused on adolescence and less is known about the important environmental contexts in young adulthood. Using data from the young adult wave of the Finnish Twin Study, FinnTwin12 ( N = 3402), we used biometric twin modeling to test whether education moderated genetic risk for alcohol use as assessed by drinking frequency and intoxication frequency. Education is important because it offers greater access to personal resources and helps determine one’s position in the broader stratification system. Results from the twin models show that education did not moderate genetic variance components and that genetic risk was constant across levels of education. Instead, education moderated environmental variance so that under conditions of low education, environmental influences explained more of the variation in alcohol use outcomes. The implications and limitations of these results are discussed. [ABSTRACT FROM AUTHOR]

The definition of anorexia nervosa was revised for the Fifth Edition of the Diagnostic and Statistical Manual (DSM-5). We examined the impact of these changes on the prevalence and prognosis of anorexia nervosa. In a nationwide longitudinal study of Finnish twins born 1975–1979, the women (N = 2825) underwent a 2-stage screening for eating disorders at mean age 24. Fifty-five women fulfilled DSM-IV criteria for lifetime anorexia nervosa. When we recoded the interviews using DSM-5 criteria, we detected 37 new cases. We contrasted new DSM-5 vs. DSM-IV cases to assess their clinical characteristics and prognosis. We also estimated lifetime prevalences and incidences and tested the association of minimum BMI with prognosis. We observed a 60% increase in the lifetime prevalence of anorexia nervosa using the new diagnostic boundaries, from 2.2% to 3.6%. The new cases had a later age of onset (18.8 y vs. 16.5, p = 0.002), higher minimum BMI (16.9 vs. 15.5 kg/m 2 , p = 0.0004), a shorter duration of illness (one year vs. three years, p = 0.002), and a higher 5-year probability or recovery (81% vs. 67%, p = 0.002). Minimum BMI was not associated with prognosis. It therefore appears that the substantial increase in prevalence of anorexia nervosa is offset by a more benign course of illness in new cases. Increased diagnostic heterogeneity underscores the need for reliable indicators of disease severity. Our findings indicate that BMI may not be an ideal severity marker, but should be complemented by prognostically informative criteria. Future studies should focus on identifying such factors in prospective settings. [ABSTRACT FROM AUTHOR]

Leisure-time physical activity is a key contributor to physical and mental health. Yet the role of physical activity in modulating cortical function is poorly known. We investigated whether precognitive sensory brain functions are associated with the level of physical activity. Physical activity history (3-yr-LTMET), physiological measures and somatosensory mismatch response (sMMR) in EEG were recorded in 32 young healthy twins. In all participants, 3-yr-LTMET correlated negatively with body fat%, r = −0.77 and positively with VO 2max , r = 0.82. The fat% and VO 2max differed between 15 physically active and 17 inactive participants. Trend toward larger sMMR was seen in inactive compared to active participants. This finding was significant in a pairwise comparison of 9 monozygotic twin pairs discordant for physical activity. Larger sMMR reflecting stronger synchronous neural activity may reveal diminished gating of precognitive somatosensory information in physically inactive healthy young men compared to the active ones possibly rendering them more vulnerable to somatosensory distractions from their surroundings. [ABSTRACT FROM AUTHOR]

Objective: Some studies indicate an association between napping and increased risk of type 2 diabetes. We studied this prospectively in a sample representative of general population.Methods: A questionnaire was administered to the Finnish Twin Cohort in 1990 (response rate 77%, age 33-60 years). The study population included 12,244 subjects who replied to the question "Do you sleep during the daytime (take naps)?" with five response alternatives ranging from "no need" to "every or almost every day." Information on incident cases of diabetes was obtained by linkage to nationwide registers. Logistic regression models were used to obtain odds ratios (ORs) (95% confidence intervals) for incident type 2 diabetes risk in 1991-2004 by napping category. Adjustments were made for 11 socio-demographic and lifestyle covariates. For subjects aged 33-45 years at baseline, a questionnaire in 2011 provided information on prevalent diabetes.Results: Thirty-four per cent had no need for napping, and 15% did so on ≥3 days weekly. There were 356 incident type 2 diabetes cases during the follow-up. Using the 'no need' category as the reference, the risk of type 2 diabetes was significantly increased only among those napping most frequently [OR 1.86 (1.29-2.67), age- and sex-adjusted]. After adjusting for other covariates, the results were essentially the same, but when adjusted for body mass index, the association decreased (to about 1.3) and was statistically non-significant. Analysis of 2011 self-reported type 2 diabetes was in line with the register data.Conclusions: Frequent napping is associated with future risk of type 2 diabetes. This association is largely explained by obesity. [ABSTRACT FROM AUTHOR]

Background: This study investigated how cigarette smoking and alcohol use predict disability retirement.Methods: Data from the longitudinal nationwide Finnish Twin Cohort study were analyzed, with clustered study design applied when computing 95% confidence intervals (CI). The sample included 21,719 individuals. Smoking and alcohol use were assessed with a questionnaire in 1975. Registry data on retirement events up till end of 2004 were obtained from the Social Insurance Institution and the Finnish Centre for Pensions.Results: Disability pension was granted to 4251 participants. Among men, adjusted for age and alcohol use, former (HR=1.45, 95%CI 1.28, 1.65, p<.001) and daily smokers (HR=1.93, 95%CI 1.71, 2.17, p<.001) showed elevated disability pension risk compared to never smokers. Among women, daily smokers (HR=1.25, 95%CI 1.11, 1.40, <.001) had elevated risk. The age and smoking adjusted risk estimates for alcohol were elevated among abstainers (men HR=1.41, 95%CI 1.21, 1.65, p<.001; women HR=1.36, 95%CI 1.23, 1.52, p<.001) and heavy drinkers (men HR=1.30, 95%CI 1.18, 1.43, p<.001; women HR=1.34, 95%CI 1.04, 1.72, p=.026). Those being persistent smokers and binge drinkers had over three-fold disability risk compared to those who were binge drinkers but had only a few smoking years (men: HR=3.32, 95%CI 2.43, 4.54, p<.001; women: HR=4.05, 95%CI 2.05, 8.00, p<.001). Among men and women who were not binge drinkers, longer smoking duration was needed for elevated disability risk.Conclusions: Both smoking and excess alcohol use significantly predict disability retirement. In order to extend working careers, more attention should be paid to health behaviors, in addition to working conditions. [ABSTRACT FROM AUTHOR]

Major depression is associated with alterations in the auditory P3 event-related potential (ERP). However, the persistence of these abnormalities after recovery from depressive episodes, especially in young adults, is not well known. Furthermore, the potential influence of substance use on this association is poorly understood. Young adult twin pairs (N = 177) from the longitudinal FinnTwin16 study were studied with a psychiatric interview, and P3a and P3b ERPs elicited by task-irrelevant novel sounds and targets, respectively. Dyadic linear mixed-effect models were used to distinguish the effects of lifetime major depressive disorder from familial factors and effects of alcohol problem drinking and tobacco smoking. P3a amplitude was significantly increased and P3b latency decreased, in individuals with a history of lifetime major depression, when controlling the fixed effects of alcohol abuse, tobacco, gender, twins' birth order, and zygosity. These results suggest that past lifetime major depressive disorder may be associated with enhanced attentional sensitivity. • Attention and past lifetime major depressive disorder studied in young adult twins. • Influences of alcohol drinking and tobacco smoking were controlled. • Major depression history associated with enhanced auditory P3a and accelerated P3b. • Effects of major depression could increase the sensitivity of auditory attention. [ABSTRACT FROM AUTHOR]

Background: Disturbed sleep is associated with mood disorders. Both depression and insomnia may increase the risk of disability retirement. The longitudinal links among insomnia, depression and work incapacity are poorly known.Methods: We examined association of self-reported sleep quality with incident symptoms of depression and disability retirement due to depressive disorders in a longitudinal population-based sample of twins (n=12,063 individuals). These adults were categorized by their sleep quality in 1975 and 1981, excluding individuals with depressed mood in 1975/1981. The outcomes were the Beck Depression Inventory (BDItot) and its subscale Negative Attitudes Towards Self (BDINATS) in 1990 as dichotomized measures, and the incidence of disability retirement due to depressive disorder during 1991-2004.Results: Onset of poor sleep between 1975 and 1981 predicted incident depression (BDItot OR=4.5, 95% CI: 2.7-7.4, BDINATS OR=2.0, 95% CI: 1.4-2.7), while persistent poor sleep showed somewhat weaker effects (BDItot; OR=2.5, 95% CI: 1.0-6.0, BDINATS OR=1.9, 95% CI: 1.1-3.3). Among those with few recent stressful life events, onset of poor sleep predicted strongly depression (BDINATS OR=9.5, 95% CI: 3.7-24.2). Likewise onset of poor sleep by 1981 increased the risk of disability retirement due to depression (OR=2.9, 95% CI: 1.8-4.9) with a similar risk among those with persistent poor sleep (OR=2.7, 95% CI: 1.3-5.7).Limitations: Lack of baseline diagnostic interviews; sleep quality based on self-report.Conclusions: Poor sleep is of importance in etiology of depression and disability retirement due to depression. This emphasizes the importance of early detection and treatment of sleep disturbances. [ABSTRACT FROM AUTHOR]

Abstract: Introduction: Low socio-economic status (SES) is strongly related to smoking, but studies examining the association of SES with nicotine dependence (ND) are scarce. The aim of this study was to examine the associations of SES and marital status with smoking, multiple measures of ND, and cotinine as a nicotine intake biomarker. Methods: The sample comprised 1746 ever smokers, sampled from the National FINRISK 2007 Study, who had completed a tobacco specific questionnaire in addition to the standard clinical examination. The Fagerström Test for Nicotine Dependence (FTND), the Heaviness of Smoking Index (HSI), the Nicotine Dependence Syndrome Scale (NDSS), and the Hooked On Nicotine Checklist (HONC) were assessed, while plasma cotinine was measured as a biomarker of nicotine exposure in daily smokers. Univariate and multivariate associations were assessed by linear regression and multinomial logistic regression. Results: In multivariate models, lower education was associated with higher FTND and HSI, income with HSI, and occupation with HSI (men only), FTND, HONC and NDSS scores. Lower education was related to higher cotinine levels among daily smokers, although the association diminished slightly after adjusting for daily smoking amount. Living without a spouse was associated with daily smoking and higher ND. Conclusion: In this cross-sectional study low SES was linked with higher ND among current smokers, while low SES was associated with higher cotinine levels among daily smokers. Living alone was linked with higher ND. Longitudinal studies are warranted to further explore these associations. As lower SES smokers are more addicted they may need more targeted cessation services to succeed in quitting smoking. [Copyright &y& Elsevier]

Abstract: Background: Adolescent substance use is associated with lower educational achievement but the directionality of the association remains uncertain. We analyzed data on drinking, smoking and educational achievement to study the associations between substance use and education from early adolescence to young adulthood. Methods: Longitudinal data from four time points (ages 12, 14, 17, and 19–27 years) from a population-based cohort study of Finnish twin individuals were used to estimate bivariate cross-lagged path models for substance use and educational achievement, adjusting for sex, parental covariates, and adolescent externalizing behavior. A total of 4761 individuals (49.4% females) were included in the analyses. Educational achievement was assessed with teacher-reported grade point average at ages 12 and 14, and with self-reported student status and completed education at age 17 and in young adulthood. From self-reported questionnaire items, frequency of any drinking, frequency of drinking to intoxication, any smoking and daily smoking were analyzed. Results: Alcohol use and smoking behaviors at ages 12 and 14 predicted lower educational achievement at later time points even after previous achievement and confounding factors were taken into account. Lower school achievement in adolescence predicted a higher likelihood of engaging in smoking behaviors but did not predict later alcohol use. Higher educational attainment at age 17 predicted more frequent drinking in young adulthood. Conclusions: Adolescent drinking behaviors are associated with lower future educational achievement independently of prior achievement, whereas smoking both predicts and is predicted by lower achievement. Early substance use indexes elevated risk for poor educational outcomes. [Copyright &y& Elsevier]

Abstract: Objective: Little is known about the associations of serum fatty acids with lipoprotein profile and the underlying genetic and environmental etiology of these relationships. We aimed to analyze the phenotypic association of serum n-6 and n-3 polyunsaturated (PUFAs), monounsaturated (MUFAs) and saturated (SFAs) fatty acids (relative proportion to total fatty acids) with lipids and lipoproteins, and to quantify common genetic and environmental factors determining their covariation. Methods: Two cohorts of healthy Finnish twins were assessed in young adulthood. Data were available for 1269 individual twins including 561 complete pairs. Serum metabolites were measured by nuclear magnetic resonance spectroscopy. Bivariate quantitative genetic models were used to decompose the phenotypic covariance between the pairs of traits into genetic and environmental components. Results: Among the strongest correlations observed, serum total n-6 PUFAs and linoleic acid were inversely (max. r = −0.65) and MUFAs positively (max. r = 0.63) correlated with triglycerides and very low-density lipoprotein (VLDL) particle concentration, particularly with large VLDL (for n-6 PUFAs) and medium VLDL (for MUFAs). Genetic factors significantly contributed to their covariance with bivariate heritability estimates ranging from 44% to 56% for n-6 PUFAs and 58% to 66% for MUFAs. Genetic correlations with lipid traits were moderate to high (max. r A = −0.59 and 0.70 for n-6 PUFAs and MUFAs, respectively). Statistically significant, but substantially weaker phenotypic correlations of total n-3 PUFAs, docosahexaenoic acid (DHA) and SFAs with lipoprotein profile were not decomposed into their genetic and environmental components. Conclusion: Shared genetic factors are important in explaining why higher concentrations of serum n-6 PUFAs and lower concentrations of serum MUFAs strongly associate with lower triglyceride and VLDL particle concentrations. [Copyright &y& Elsevier]

Abstract: Background: Few twin studies have examined nutrition-related phenotypes among children, and none has investigated energy and macronutrient intakes. Objective: The objective was to quantify genetic and environmental influences on variations in energy and macronutrient intakes among children aged 9years. Design: We conducted a nutrition study among children participating in the Quebec Newborn Twin Study, a population-based birth cohort of twins. We derived dietary data from two multiple-pass 24-hour dietary recalls with a parent and his or her child. The analysis employed a classic twin study design and used data from 379 twin pairs. Results: Univariate analyses indicate that heritability for mean daily energy (kcal) and macronutrient (g) intakes was moderate, ranging from 0.34 (95% CI: 0.22, 0.46) to 0.42 (0.31, 0.53). Genetic effects also accounted for 0.28 (0.16, 0.40) of the variance in percent of energy from lipids, while only environmental (shared and unique) effects accounted for the variance in percent of energy from proteins and carbohydrates. The shared environment did not contribute to variations in daily intakes for most of the nutritional variables under study. Multivariate analyses suggest the presence of macronutrient-specific genetic influences for lipids and carbohydrates, estimated at 0.12 (0.04, 0.19) and 0.20 (0.11, 0.29) respectively. Conclusions: The unique environment (i.e., not shared by family members) has the largest influence on variances in daily energy and macronutrient intakes in 9-year-old children. This finding underscores the need to take obesogenic environments into account when planning dietary interventions for younger populations. [Copyright &y& Elsevier]

Abstract: Objective: Little is known about the association of mild symptoms and mental well-being with risk of disability pension (DP) due to somatic diagnoses, even less for DP due to low back diagnoses (LBD). Moderate genetic influences on personality traits, life dissatisfaction and DP exist suggesting that shared genetic influences may underlie these associations. One can control for familial confounding (genetics and family environment) by examining twins. This twin study aimed to investigate personality traits and life dissatisfaction as predictors for DP due to LBD accounting for familial confounding. Methods: Data on 24043 twins aged 18–65year in a baseline survey in 1975 was followed up from national DP register data until 2004. Personality traits were assessed using the short version of the Eysenck Personality Inventory and life dissatisfaction was measured with a four item scale on levels of interest, happiness, easiness, and loneliness of life. Cox proportional hazards regression was used to calculate hazard ratios (HR) with 95% confidence intervals (CI). Results: DP due to LBD was granted to 537 individuals during the follow-up. Each one unit increase in life dissatisfaction (HR 1.06; 95%CI 1.03, 1.10) and neuroticism (1.07; 1.03, 1.10) but not extroversion was significantly associated with an elevated risk for DP due to LBD. These associations with life dissatisfaction and neuroticism remained when socioeconomic status, education, and marital status were taken into account, and demonstrated an independence from familial confounding. Conclusion: Life dissatisfaction and neuroticism seems to be early, perhaps causal risk factors for DP due to LBD. [Copyright &y& Elsevier]

Epicardial fat with its close proximity to coronary arteries has been suggested to be a significant predictor of cardiovascular disease. We studied the relations among acquired obesity, low-grade inflammation, and genetic factors in the accumulation of epicardial fat. A rare sample (n = 15) of healthy monozygotic (MZ) twin pairs discordant for obesity (intrapair difference in body mass index ≥3 kg/m2) and 9 concordant MZ pairs 23 to 33 years old were examined for cardiac structure, function, epicardial fat thickness (echocardiography), abdominal subcutaneous tissue, and visceral adipose tissue (VAT), liver fat (magnetic resonance imaging/spectroscopy), and serum high-sensitivity C-reactive protein. In the entire sample, MZ cotwins were remarkably similar in most echocardiographic measurements including epicardial fat (intraclass correlation 0.63, p = 0.0004). However, in the discordant pairs, the obese cotwins (16.5 kg, 23% heavier) had 26% more epicardial fat (p = 0.0029) than nonobese cotwins. They also had significantly larger atrial and left ventricular dimensions. Epicardial fat correlated with VAT (r = 0.49, p = 0.02) in individual twins and when using intrapair differences of measurements within pairs (r = 0.39, p = 0.06). In multiple regression analyses including abdominal subcutaneous tissue, VAT, and liver fat, high-sensitivity C-reactive protein was the only factor that remained significantly associated with epicardial fat in individual twins and within pairs. In conclusion, subjects who share the same genes seem to have similar cardiac dimensions. However, acquired obesity increases epicardial fat independent of genetic factors. The close relation between epicardial fat and low-grade inflammation is likely to contribute to the development of cardiovascular disease in obesity. [ABSTRACT FROM AUTHOR]

Abstract: Stress has been suggested to reduce survival after cancer, but the results of previous studies have been contradictory. We investigated the hypothesis in a national cohort of adults in Finland. Of those who completed the Stressful Life Events scale and the Stress of Daily Activities scale, 1470 and 1882, respectively, later had cancer and were included in the analysis, covering 23 years of follow-up between 1982 and 2004. In Cox regression analysis, the multivariate hazard ratio (HR) was 0.99 (95% confidence interval [CI], 0.96–1.01) for total number of life events and the HR for the life change score was 0.99 (95% CI, 0.95–1.03). Further, the HR was 0.92 (95% CI, 0.69–1.22) for severe daily stress. Overall, the results of the current study do not support the hypothesis that stress reduces cancer survival. [Copyright &y& Elsevier]

Abstract: Background: Studies on diet and high-density lipoprotein (HDL) subspecies distribution are limited. Objective: We examined the relationship between macronutrient composition and lipoprotein particle size and HDL subspecies independent of genetic effects by studying monozygotic (MZ) twins. Methods: 24 healthy MZ twin pairs aged 23–33 years were identified from two longitudinal population-based studies, FinnTwin16 and FinnTwin12. Total energy and nutrient intake were assessed with 3-day food records and physical activity was measured by the Baecke index. HDL subspecies distribution was determined by non-denaturing gradient gel electrophoresis. Associations between diet composition and HDL mean particle size were determined by multivariate nutrient density models adjusted for confounding variables. Results: Substituting one energy percentage from omega-3 polyunsaturated fatty acids (n-3 PUFAs) for a corresponding amount of energy from other type of fats was related to changes in the relative proportions of the HDL subspecies 2b, 3a and 3b toward a larger mean particle size in men (β ±SE: 1.00±0.26nm, p =0.004) and women (β ±SE: 0.90±0.21nm, p =0.001). This association remained significant in analyses controlling for genetic and shared environmental influences using within-pair differences of the measures in MZ twin pairs (β ±SE: 0.37±0.14nm, p =0.019). Twins with the higher n-3 PUFA intake had significantly higher proportions of large HDL2b particles and lower proportions of smaller-sized HDL3a and HDL3b particles as compared to their co-twins with lower intakes (p <0.05). Conclusions: Our data suggest that n-3 PUFA intake is associated with a favorable change in the distribution of HDL subspecies towards larger particles independent of genetic and shared environmental factors. [Copyright &y& Elsevier]

Background & Aims: Ectopic fat in muscle and liver is linked to obesity and type 2 diabetes. Recently, pancreatic lipid accumulation has also been associated with β-cell dysfunction and reduced insulin production, leading to the development of type 2 diabetes. Physical exercise training has been shown to attenuate β-cell dysfunction in patients, but little is known about its effects on pancreatic and hepatic fat accumulation. In this study, we validated in-vivo proton magnetic resonance spectroscopy (1H MRS) in pancreatic fat measurement with biochemical measurements in a pig model. Thereafter, the effects of increased physical activity on the amounts of pancreatic and liver fat were studied in eight monozygotic twin pairs who have discordant physical activity and fitness. Methods: Pancreatic fat content was studied in 15 pigs using 1H MRS and/or biochemical analyses. In addition, liver and pancreatic fat were assessed using 1H MRS in eight monozygotic male twin pairs with 18% mean difference in VO2max between the twin brothers. Results: Twins with higher physical fitness had 23% less liver fat (1.3±1.3% vs. 2.1±2.6%, p =0.022) but no such difference was observed in the pancreatic fat (8.2±9.3% vs. 9.8±8.5%, respectively, p =0.3). Hepatic fat content was inversely associated with VO2max. A positive association was found between pancreatic and liver fat contents (β =5.18, p =0.012). Pancreatic fat content was also associated with insulin sensitivity indexes and plasma adiponectin and glutamyltransferase concentrations. Conclusions: Pancreatic fat content is associated with insulin resistance and hepatic fat content. An active lifestyle seems to beneficially influence hepatic fat metabolism. [Copyright &y& Elsevier]

Summary: Studies of singletons suggest that right-handed individuals may have higher levels of testosterone than do left-handed individuals. Prenatal testosterone levels are hypothesised to be especially related to handedness formation. In humans, female members from opposite-sex twin pairs may experience elevated level of prenatal exposure to testosterone in their intrauterine environment shared with a male. We tested for differences in rates of left-handedness/right-handedness in female twins from same-sex and opposite-sex twin pairs. Our sample consisted of 4736 subjects, about 70% of all Finnish twins born in 1983–1987, with information on measured pregnancy and birth related factors. Circulating testosterone and estradiol levels at age 14 were available on 771 and 744 of these twins, respectively. We found significantly (p =.006) lower prevalence of left-handedness in females from opposite-sex pairs (5.3%) compared to females from same-sex pairs (8.6%). The circulating levels of neither testosterone nor estradiol related to handedness in either females or males. Nor were there differences in circulating testosterone or estradiol levels between females from opposite-sex and same-sex twin pairs. Birth and pregnancy related factors for which we had information were unrelated to handedness. Our results are difficult to fully explain by postnatal factors, but they offer support to theory that relates testosterone to formation of handedness, and in a population-based sample, are suggestive of effects of prenatal testosterone transfer. [ABSTRACT FROM AUTHOR]