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STUDY QUESTION Is there a relation between ART and DNA methylation (DNAm) patterns in cord blood, including any differences between IVF and ICSI? SUMMARY ANSWER DNAm at 19 CpGs was associated with conception via ART, with no difference found between IVF and ICSI. WHAT IS KNOWN ALREADY Prior studies on either IVF or ICSI show conflicting outcomes, as both widespread effects on DNAm and highly localized associations have been reported. No study on both IVF and ICSI and genome-wide neonatal DNAm has been performed. STUDY DESIGN, SIZE, DURATION This was a cross-sectional study comprising 87 infants conceived with IVF or ICSI and 70 conceived following medically unassisted conception. The requirement for inclusion in the study was an understanding of the Swedish language and exclusion was the use of donor gametes. PARTICIPANTS/MATERIALS, SETTING, METHODS Participants were from the UppstART study, which was recruited from fertility and reproductive health clinics, and the Born into Life cohort, which is recruited from the larger LifeGene study. We measured DNAm from DNA extracted from cord blood collected at birth using a micro-array (450k array). Group differences in DNAm at individual CpG dinucleotides (CpGs) were determined using robust linear models and post-hoc Tukey’s tests. MAIN RESULTS AND THE ROLE OF CHANCE We found no association of ART conception with global methylation levels, imprinted loci and meta-stable epialleles. In contrast, we identify 19 CpGs at which DNAm was associated with being conceived via ART (effect estimates: 0.5–4.9%, PFDR < 0.05), but no difference was found between IVF and ICSI. The associated CpGs map to genes related to brain function/development or genes connected to the plethora of conditions linked to subfertility, but functional annotation did not point to any likely functional consequences. LIMITATIONS, REASONS FOR CAUTION We measured DNAm in cord blood and not at later ages or in other tissues. Given the number of tests performed, our study power is limited and the findings need to be replicated in an independent study. WIDER IMPLICATIONS OF THE FINDINGS We find that ART is associated with DNAm differences in cord blood when compared to non-ART samples, but these differences are limited in number and effect size and have unknown functional consequences in adult blood. We did not find indications of differences between IVF and ICSI. STUDY FUNDING/COMPETING INTEREST(S) E.W.T. was supported by a VENI grant from the Netherlands Organization for Scientific Research (91617128) and JPI-H2020 Joint Programming Initiative a Healthy Diet for a Healthy Life (JPI HDHL) under proposal number 655 (PREcisE Project) through ZonMw (529051023). Financial support was provided from the European Union’s Seventh Framework Program IDEAL (259679), the Swedish Research Council (K2011-69X-21871-01-6, 2011-3060, 2015-02434 and 2018-02640) and the Strategic Research Program in Epidemiology Young Scholar Awards, Karolinska Institute (to A.N.I.) and through the Swedish Initiative for Research on Microdata in the Social And Medical Sciences (SIMSAM) framework grant no 340-2013-5867, grants provided by the Stockholm County Council (ALF-projects), the Strategic Research Program in Epidemiology at Karolinska Institutet and the Swedish Heart-Lung Foundation and Danderyd University Hospital (Stockholm, Sweden). The funders had no role in study design, data collection, analysis, decision to publish or preparation of the manuscript. The authors declare no competing interests. TRIAL REGISTRATION NUMBER N/A.

The study aimed to investigate if assisted reproductive technology (ART) treatment or a diagnosis of infertility were associated with the risk of ovarian cancer or borderline ovarian tumors (BOT) in parous women. In a population-based register study of 1,340,097 women with a first live birth in Sweden 1982–2012, the relationship between ART treatments, infertility and incidence of ovarian cancer or BOT were investigated using Cox regression analysis. In the cohort, 38,025 women gave birth following ART, 49,208 following an infertility diagnosis but no ART and 1,252,864 without infertility diagnosis or ART. During follow-up, 991 women were diagnosed with ovarian cancer and 747 with BOT. Women who gave birth following ART had higher incidence of both ovarian cancer (adjusted hazard ratio [aHR] 2.43, 95% confidence interval [CI] 1.73–3.42) and BOT (aHR 1.91, 95% CI 1.27–2.86), compared to women without infertility. Compared to women with infertility diagnoses and non-ART births, women with ART births also had a higher incidence of ovarian cancer (aHR 1.79, 95% CI 1.18–2.71) and BOT (aHR 1.48, 95% CI 0.90–2.44). Our results suggest that women who have gone through ART have a higher risk of ovarian cancer and BOT. At least part of that risk seems to be due to the underlying infertility and not the treatment per se, since the increased risk was smaller when comparing to other infertile women. As ART treatments are becoming more common and ovarian cancer usually occur in women of advanced age, larger studies with longer follow-up are needed in order to confirm or refute our findings. Electronic supplementary material The online version of this article (10.1007/s10654-019-00540-3) contains supplementary material, which is available to authorized users.

Some studies have suggested that infertility is a risk factor for endometrial, ovarian and breast cancer. The study aimed to create a comprehensive picture of the association between infertility and the risk of ovarian, endometrial and breast cancer, and whether any association could be explained by ovulatory disturbances, endometriosis or nulliparity. In a population-based cohort of 2,882,847 women, cox regression analysis was used to investigate cancer incidence among infertile women. Overall, infertility was associated with a higher incidence rate of ovarian (adjusted hazard ratio [aHR] 1.53, 95% confidence interval [CI] 1.38–1.71) and endometrial cancer (aHR 1.25, 95% CI 1.11–1.40), but not of breast cancer (aHR 0.96, 95% CI 0.92–1.01). Ovarian cancer incidence was higher in women diagnosed with endometriosis, and in nulliparous women with ovulatory disturbances, compared to women with none of the diagnoses. Endometrial cancer incidence was higher in women with ovulatory disturbances, but not in women with endometriosis. These findings suggest that infertility could have long-term consequences of importance to physicians and public health workers. Electronic supplementary material The online version of this article (10.1007/s10654-018-0474-9) contains supplementary material, which is available to authorized users.

Study Question What is the relationship with assisted reproductive technology (ART) and DNA methylation (DNAm) patterns in cord-blood and is there any difference between in vitro fertilisation (IVF) and intra-cytoplasmic sperm injection (ICSI)? Summary Answer We identify nineteen CpGs at which DNAm was associated with being conceived via assisted reproductive technology (ART). No difference was found between IVF and ICSI. What is known already Prior studies on either IVF or ICSI show conflicting outcomes as both widespread effects on DNAm and highly localized associations have been reported. No study on both IVF and ICSI and genome-wide neonatal DNAm has been performed. Study design, size, duration We measured 87 infants conceived with in vitro fertilisation (IVF) or intra-cytoplasmic sperm injection (ICSI) and 70 who were not in a cross-sectional study. Participants/materials, setting, methods Participants were from the UppstART study, which were recruited from fertility and reproductive health clinics, and the Born into Life cohort, which is created from the larger LifeGene study. We measured DNAm from DNA extracted from cord blood collected at birth with the Illumina Infinium HumanMethylation450k BeadChip micro-array. Group differences in DNA methylation at individual CpG dinucleotides (CpGs) were determined using robust linear models and post-hoc Tukey’s tests. Main results and the role of chance We found no association with global methylation levels, imprinted loci and meta-stable epialleles. In contrast, we identify nineteen CpGs at which DNA methylation was associated with being conceived via ART (effect estimates: 0.5-4.9%, PFDR Limitations, reasons for caution We measured DNAm in cord blood and not at later ages and/or other tissues and findings remain to be replicated in an independent study. Wider implications of the findings We find ART is associated with DNA methylation differences in cord blood, but these differences are limited in number, effect size and with unknown functional consequences in adult blood. We did not find indications for a disparity between IVF and ICSI. Study funding/competing interest(s) The authors declare no competing interests. The funders had no role in the study, study design, analysis and decision to publish.

Introduction Women undergoing fertility treatment experience high levels of stress. However, it remains uncertain if and how stress influences in vitro fertilization (IVF) cycle outcome. This study aimed to investigate whether self-reported perceived and infertility-related stress and cortisol levels were associated with IVF cycle outcomes. Material and methods A prospective cohort of 485 women receiving fertility treatment was recruited from September 2011 to December 2013 and followed until December 2014. Data were collected by online questionnaire prior to IVF start and from clinical charts. Salivary cortisol levels were measured. Associations between stress and cycle outcomes (clinical pregnancy and indicators of oocyte and embryo quality) were measured by logistic or linear regression, adjusted for age, body mass index, education, smoking, alcohol and caffeine consumption, shiftwork and night work. Results Ultrasound verified pregnancy rate was 26.6% overall per cycle started and 32.9% per embryo transfer. Stress measures were not associated with clinical pregnancy: when compared with the lowest categories, the adjusted odds ratio (OR) and 95% confidence interval (CI) for the highest categories of the perceived stress score was 1.04 (95% CI 0.58-1.87), infertility-related stress score was OR = 1.18 (95% CI 0.56-2.47), morning and evening cortisol was OR = 1.18 (95% CI 0.60-2.29) and OR = 0.66 (95% CI 0.34-1.30), respectively. Conclusions Perceived stress, infertility-related stress, and cortisol levels were not associated with IVF cycle outcomes. These findings are potentially reassuring to women undergoing fertility treatment with concerns about the influence of stress on their treatment outcome.

Polycystic ovary syndrome (PCOS) is an endocrine disorder affecting 5-15% of reproductive-aged women and characterized by high levels of circulating androgens. Given that androgens have been implicated in the aetiology of several psychiatric disorders, it was hypothesized that women with PCOS have high risk for psychiatric comorbidity. We aimed to investigate this risk amongst women with PCOS, as well as in their siblings, to elucidate if familial factors underlie any potential associations. Using the Swedish national registers, we identified all women diagnosed with PCOS between 1990 and 2013 (n=24,385), their full-siblings (n=25,921), plus matched individuals (1:10/100) from the general population and their full-siblings. Psychiatric disorder diagnoses were identified including schizophrenia, bipolar disorder, depressive and anxiety disorders, eating disorders, personality and gender identity disorder, autism spectrum disorder (ASD), attention-deficit hyperactivity disorder (ADHD), tics, attempted and completed suicide. Odds ratios (OR) and 95% confidence intervals (CI) were estimated using conditional logistic regression and adjusted ORs (AOR) were determined by adjustment for comorbid psychiatric disorders. Overall, women with PCOS had an increased odds of having at least one psychiatric disorder (OR=1.56 [95CI%, 1.51-1.61]). Crude ORs showed associations with nearly all psychiatric disorders included in this study. Following adjustment for comorbid psychiatric disorders, women with PCOS were still at a significantly increased risk for bulimia, schizophrenia, bipolar disorder, depressive and anxiety disorders, personality disorders, with the highest AORs for ASD (AOR=1.55 [95%CI, 1.32-1.81]) and tics (AOR=1.65 [95%CI, 1.10-2.47]). Significantly higher AORs were found for ASD in both brothers and sisters of women with PCOS, and for depressive, anxiety, and schizophrenia spectrum disorders in the sisters only. Notably, the crude ORs for attempted suicide were 40% higher in women with PCOS and 16% higher in their unaffected sisters. However, the AORs were greatly attenuated indicating that underlying psychiatric comorbidity is important for this association. Women with PCOS had higher risks for a range of psychiatric disorders not shown before. Elevated risk in their siblings suggests shared familial factors between PCOS and psychiatric disorders. This study is an important first step towards identifying the underlying mechanisms for risk of psychiatric disorders in women with PCOS. Health professionals treating women with PCOS should be aware that these patients - as well as their family members - are important targets for mental health care.

We explore the influence of co-occurring somatic illnesses on prevalent overactive bladder in women of premenopausal age.Data for the present study were derived from a nationwide survey on complex diseases among all twins in the Swedish Twin Registry born 1959 to 1985. The present study was limited to female twins participating in the survey (12,850). Generalized estimating equations were used to estimate odds ratios with 95% CIs. Environmental and genetic influences were assessed in co-twin control analysis.Generalized estimating equations analysis showed a significant association between overactive bladder and migraine (OR 1.34, 95% CI 1.15-1.57), fibromyalgia (1.83, 1.54-2.18), chronic fatigue (1.81, 1.49-2.19) and eating disorders (1.56, 1.24-1.96). There was also a significant association with allergic disorders including asthma (1.24, 1.01-1.52) and eczema (1.22, 1.04-1.43). Among reproductive disorders, urinary tract infections (1.60, 1.40-1.84), dysmenorrhea (1.53, 1.33-1.76) and pelvic pain (1.60, 1.31-1.94) showed the strongest association with overactive bladder. Results from co-twin control analysis indicated that the significant associations observed in generalized estimating equations analysis were influenced by environmental and genetic factors without a common pathway model.Our results suggest a multifactorial and complex pathogenesis of overactive bladder in which associations between various somatic illnesses and overactive bladder may be affected by environmental and genetic factors.

Attachment theory proposes that early parent–child relationships provide the basis for all future close relationships of the individual, through childhood and adolescence into later life. The purpose of the present study was to examine the relationship between parental attachment, peer attachment and students’ perceptions of their teacher’s interpersonal behaviour, in order to shed light on the channels through which these constructs relate. In doing so, we examined three proposed theoretical schemes of pre-adolescents’ representations of multiple relationships. As a side-goal, the psychometric properties of the Greek translations of the Revised Inventory of Parental and Peer Attachment (IPPA-R) and the Questionnaire on Teacher Interaction (QTI-G) were investigated. Two independent samples comprising 270 and 306 pre-adolescents (grades 5–7), respectively participated in the study. Results supported a four-factor structure of the IPPA-R and an elliptical shape for the Interpersonal Teacher Circle measured by the QTI-G. The integrative scheme regarding pre-adolescents’ multiple adult relationships was supported by the data. Parental attachment relationships were found to be an important determinant of students’ perceptions of their teacher interpersonal behaviour, which in turn mediated the relationship between parental and peer attachment relationships. Results are discussed in terms of their theoretical and practical implications.

The unique intrauterine environment has been proposed to put twins at increased risk of certain cancers compared to singletons, still large population comparisons have generally indicated lower risks in twins. To improve the understanding of potential twin influence on cancer we compared twins to their singletons siblings, to target a unique twinning influence. Singletons from twin families were contrasted to singletons from non-twin families to further capture potential twin family influence on risk of cancer. Family relations were identified using the Swedish Multi-Generation Register. Among individuals born between 1932 and 1958, 49,156 twins and N = 35,227 singletons were identified from 18,098 unique twin families. All incident cases of specific cancer types were identified in the National Cancer Register up to the end of 2007. Standardized survival functions were estimated using weighted Cox proportional hazard regression and the corresponding cumulative risks plotted against age. Overall, primary cancers were identified in 9% and 18% of all male and female twins, compared to 11% and 19% of their male and female singleton siblings. When specific cancer sites were compared using standardized cumulative risk plots, no consistent statistically significant differences were noted either between twins and singletons of twin families or between singletons of twin and non-twin families. Despite a different intrauterine experience, twinning does not seem to have any greater negative influence on life-time risks of cancer. The findings also indicate that twin family membership has no substantial influence on cancer risks.

Despite advancements in the treatment of childhood leukemia, socioeconomic status (SES) may potentially affect disease prognosis. This study aims to evaluate whether SES is associated with survival from childhood leukemia.The US National Cancer Institute Surveillance, Epidemiology and End Results Program (SEER) 1973-2010 data were analyzed; thereafter, results were meta-analyzed along with those from survival (cohort) studies examining the association between SES indices and survival from childhood leukemia (end-of-search date: 31 March 2014). Random-effects models were used to calculate pooled effect estimates (relative risks, RRs); meta-regression was also used.We included 29 studies yielding 28 804 acute lymphoblastic leukemia (ALL), 3208 acute myeloblastic leukemia (AML) and 27 650 'any' leukemia (denoting joint reporting of all subtypes) cases. According to individual-level composite SES indices, children from low SES suffered from nearly twofold higher death rates from ALL (pooled RR: 1.83, 95% confidence interval 1.00-3.34, based on four study arms); likewise, death RRs derived from an array of lower area-level SES indices ranged between 1.17 and 1.33 (based on 11 study arms). Importantly, the survival gap between higher and lower SES seemed wider in the United States, with considerably (by 20%-82%) increased RRs for death from ALL in lower SES. Regarding AML, poorer survival was evident only when area-level SES indices were used. Lastly, remoteness indices were not associated with survival from childhood leukemia.Children with lower SES suffering childhood leukemia do not seem to equally enjoy the impressive recent survival gains. Special health policy strategies and increased awareness of health providers might minimize the effects of socioeconomic disparities.

Background Women with polycystic ovary syndrome (PCOS) are at elevated risk for suffering from depression. Neuroticism is a personality trait that has been associated with an increased risk for developing major depressive disorder (MDD). The aim of the present study was to quantify and decompose the correlation between neuroticism, PCOS, and MDD into shared and unique genetic and environmental etiologies, by using quantitative genetic methods. Methods In a cohort of 12,628 Swedish female twins born from 1959 to 1985, neuroticism, PCOS identified by symptoms of hyperandrogenemia (i.e., hirsutism) and oligo- and/or anovulation, and lifetime MDD status were determined through questionnaire responses. Structural equation modeling was used to study the genetic and environmental sources of the variation within, and covariation between neuroticism, PCOS, and MDD. Results Female twins with PCOS (n = 752) had significantly higher levels of neuroticism than women without PCOS, and a 2-fold increase in odds for a lifetime prevalence of MDD. The phenotypic correlation between PCOS and MDD was 0.19, with 63% of the correlation attributable to common genetic factors between the two traits. When taking into account neuroticism, 41% was attributable to common genetic factors and 9% attributable to common environmental factors shared between all three traits, with the remainder attributable to components unique to PCOS and MDD. Conclusion There are common genetic factors between neuroticism, PCOS, and MDD; however, neuroticism shares approximately half of the genetic and environmental components behind the phenotypic correlation between PCOS and MDD, providing some etiological evidence behind the comorbidity between PCOS and depression.

Whether hyperthyroidism influences the birth characteristics of children born several years after treatment is unknown.The objective of the study was to compare birth characteristics in singleton newborns delivered by women previously treated for Graves' disease (GD), toxic nodular goiter (TNG), or nontoxic goiter (NTG).This was a nested case-control design within a national cohort registry study from 1950 through 2006.The study was conducted at a university and a hospital center in collaboration.The birth characteristics of newborns (n = 3421) delivered in a cohort of 43 633 women treated for GD or toxic nodular goiter by radioiodine or surgery (exposed group) at least 1 year prior to pregnancy were compared with newborns (n = 2914) of 45 655 mothers, previously operated for NTG (unexposed group).The primary outcome was birth weight, length, and head circumference. The secondary outcome was malformations, gestational age, and type of hyperthyroidism.The birth weight of exposed children was 3431 ± 607 g (mean ± SD) compared with the unexposed, 3520 ± 641 g (P.001). The cumulative odds ratio (OR) for lower birth weight was 1.29 [95% confidence interval (CI) 1.16-1.43]. The average birth length for the exposed children was 50.0 ± 2.7 cm compared with the unexposed of 50.4 cm ± 2.6 cm (P.01) [cumulative OR 1.25 (95% CI 1.13-1.37)]. The head circumference was 34.5 ± 1.9 cm among exposed and 34.7 ± 1.8 cm, respectively (P.001), with an OR of 1.24 (95% CI 1.13-1.35). No differences in birth characteristics were observed between children born after maternal GD or toxic nodular goiter.Previous GD or TNG may influence the birth characteristics several years after radioiodine or surgical treatment.

PurposeThe Uppsala–Stockholm Assisted Reproductive Techniques (UppStART) study is a prospectively recruited sample of couples undergoing assisted reproduction in Stockholm and Uppsala county in Sweden. The study was initiated to (1) investigate possible changes in the epigenetic profile of infants inferred through the ART procedures and their consequence and (2) to assess the impact of lifestyle and health exposures on treatment outcome.ParticipantsRecruitment took place between September 2011 and December 2013, and in vitro fertilisation (IVF) cycles initiated and pregnancies conceived during this time were followed until December 2014. The cohort includes 971 participants (n= 514 women; n= 457 men), and 129 pregnancies were achieved from the first IVF cycle included in the study.Findings to dateSelf-reported demographic, health and lifestyle data were collected from a baseline questionnaire, and to assess changes to lifestyle, a follow-up questionnaire was issued at the time of oocyte retrieval, and at subsequent IVF cycles. Questionnaire data were linked to data extracted from medical records. Biological samples were collected at baseline: blood for extraction of serum, plasma and DNA, morning and evening saliva samples for cortisol measurement and at delivery including samples of maternal blood, placenta and amniotic fluid, and cord blood for epigenetic analysis.Future plansThrough the unique identification number assigned to each Swedish citizen at birth or immigration, UppStART study participants will be linked to the Swedish population-based national and quality registers to provide data from prenatal, obstetrical, neonatal and infant care, and subsequent updates will provide data on childhood health and educational outcomes. Collaboration and use of UppStART data is encouraged, and more information about access can be found at www.ki.se/meb/uppstart

Objective To investigate the association between a history of gestational diabetes mellitus (GDM) and overactive bladder (OAB) in women of premenopausal age. Design Population-based study. Setting The Swedish Twin Register. Population In 2005, a total of 14 094 female twins born between 1959 and 1985 in the Swedish Twin Registry participated in a comprehensive survey on common exposures and complex diseases. Structured questions provided information on GDM and OAB. The present study was designed as a cross-sectional analysis including all women in the cohort having given birth before 2005 (n = 7855). Methods A logistic regression model based on generalised estimating equations was used to derive odds ratios (ORs). Main outcome measure The association between a history of GDM and OAB was estimated using ORs with 95% confidence intervals (CIs). Results The prevalence of OAB in women with a history of GDM was 19.1% compared with 10.7% in women without GDM. This corresponded to a two-fold increased odds of OAB in women with a history of gestational diabetes (OR 2.13, 95% CI 1.48–3.05). After adjusting the analysis for age, body mass index, parity, smoking, and diabetes mellitus, having had GDM was associated with doubled odds of OAB (OR 1.88, 95% CI 1.26–2.80). Conclusions A history of GDM was positively associated with OAB among women of premenopausal age. The association does not seem to be mediated by body mass index or type-I or type-II diabetes mellitus.

Does the intergenerational influence on birthweight and birth length remain within female dizygotic and monozygotic twin pairs?The intergenerational influence on birthweight and birth length remained within dizygotic but not within monozygotic twin pairs.Low birthweight is associated with increased morbidity and mortality in both the short and long term; therefore it is important to understand determinants of fetal growth. There is a known intergenerational association between parents' and offspring's size at birth.This is a register-based cohort study with a nested within-twin-pair comparison. The study is retrospective, but based on prospectively collected information. The study population included 8685 monozygotic and like-sexed dizygotic female twins born in Sweden from 1926 to 1985, who had given birth to their first infant between 1973 and 2009.This study is set in Sweden and used data from the Swedish Twin Register and the Swedish Medical Birth Register. We used generalized estimating equations to obtain regression coefficients with 95% confidence intervals (CI) for the outcomes: offspring birthweight and birth length. To control for genetic and shared environmental factors, we performed within-twin-pair analyses in 1479 dizygotic and 1526 monozygotic twin pairs.In the cohort of both dizygotic and monozygotic twins, there was an association between mother's and offspring's size at birth. Within-dizygotic twin pairs, a 500-g increase from the twin pair's mean birthweight was associated with increased offspring birthweight [70 g (95% CI: 35-106)] and birth length [0.22 cm (95% CI: 0.07-0.38)]. The corresponding increase in birth length of 1 cm was estimated to increase offspring's birthweight by 26 g (95% CI: 12-40) and birth length by 0.11 cm (95% CI: 0.04-0.17). Within-monozygotic twin pairs there were no such associations.This study is limited to twins who themselves or whose co-twin voluntarily responded to questionnaires.The intergenerational influence on size at birth is suggested to be due to direct or indirect genetic factors.

Background Ovarian stimulation drugs, in particular hormonal agents used for controlled ovarian stimulation (COS) required to perform in vitro fertilization, increase estrogen and progesterone levels and have therefore been suspected to influence breast cancer risk. This study aims to investigate whether infertility and hormonal fertility treatment influences mammographic density, a strong hormone-responsive risk factor for breast cancer. Methods Cross-sectional study including 43,313 women recruited to the Karolinska Mammography Project between 2010 and 2013. Among women who reported having had infertility, 1576 had gone through COS, 1429 had had hormonal stimulation without COS and 5958 had not received any hormonal fertility treatment. Percent and absolute mammographic densities were obtained using the volumetric method Volpara™. Associations with mammographic density were assessed using multivariable generalized linear models, estimating mean differences (MD) with 95 % confidence intervals (CI). Results After multivariable adjustment, women with a history of infertility had 1.53 cm3 higher absolute dense volume compared to non-infertile women (95 % CI: 0.70 to 2.35). Among infertile women, only those who had gone through COS treatment had a higher absolute dense volume than those who had not received any hormone treatment (adjusted MD 3.22, 95 % CI: 1.10 to 5.33). No clear associations were observed between infertility, fertility treatment and percent volumetric density. Conclusions Overall, women reporting infertility had more dense tissue in the breast. The higher absolute dense volume in women treated with COS may indicate a treatment effect, although part of the association might also be due to the underlying infertility. Continued monitoring of cancer risk in infertile women, especially those who undergo COS, is warranted. Electronic supplementary material The online version of this article (doi:10.1186/s13058-016-0693-5) contains supplementary material, which is available to authorized users.

Background Studies in twins may be questioned with respect to their representativeness of the general population, not least considering the potential importance of the fetal environment for future health and disease. To better understand the influence twinning may have on health, we investigated long-term health outcomes of twins, their singleton siblings and singletons from the population. Methods Morbidity and mortality in twins was contrasted to that of their singleton siblings. These singletons from families with twins were then compared with singletons of the population to further reveal potential twin family influences on health. Familial relations were identified through the Swedish Multi-Generation Register. Among individuals born between 1932 and 1958, the number of twins and their singleton siblings identified were 49,156 and 35,277, respectively. Outcomes were incident overall cancer, cardiovascular disease (CVD) and death, identified in national registers. Standardized survival functions were estimated using Cox proportional hazards regression and the corresponding cumulative risks plotted against age. Results Cumulative risks of cancer, CVD and death in twins did not differ from singletons of families with twins, who in turn were found to be similar to singletons of families without twins. As could be expected from these findings, no differences in risks were found when twins were compared with singletons of the population. Conclusions Despite their adverse intrauterine experience, twins do not seem to fare worse than singletons with respect to adult morbidity and mortality. The findings indicate that the unique experience of twinning does not lead to adverse long-term health outcomes.

([95% CI: -1%, 82%]; P = 0.06), and every 10-mm increase in head circumference was related to a 17% greater risk of polio ([95% CI: 5%, 31%]; P = 0.004). In co-twin control analyses among 226 disease-discordant twins, birth length, birthweight and head circumference were 0.3 cm (P = 0.19), 84 g (P = 0.07) and 3 mm (P = 0.08) higher in cases than controls, respectively. Similar associations were observed among monozygotic (n = 84) and dizygotic (n = 142) twins. These findings suggest that early intrauterine growth restriction may be inversely related to the incidence of polio.

OBJECTIVES Previous studies suggest that maternal smoking during pregnancy is associated with elevated offspring blood pressure during childhood. We aimed to investigate whether this association remained in late adolescence and, if so, whether it could be attributed to an intrauterine effect or to familial confounding. METHODS We used a national cohort of 87,223 young Swedish men born between 1983 and 1988 with information on both maternal smoking during pregnancy and blood pressure at military conscription. The cohort included 780 full brothers discordant for maternal smoking. Generalized estimation equations were used to estimate regression coefficients (β) with 95% confidence intervals (95% CIs). RESULTS We found a small but significant increase in both SBP and DBP for young men whose mothers had been daily smokers during pregnancy compared with sons of nonsmoking mothers: 0.26 (95% CI 0.09 to 0.44) and 0.45 mmHg (95% CI 0.31 to 0.59) for SBP and DBP, respectively. In a within-sibling analysis comparing full brothers discordant for maternal smoking exposure, point estimates were similar but not statistically significant: 0.85 (95% CI -0.19 to 1.90) for DBP and 0.81 (-0.56 to 2.19) for SBP. CONCLUSION Maternal smoking during pregnancy is associated with a small but statistically significant increase in offspring blood pressure in late adolescence. Because the association does not appear to be explained by familial confounding, our results support an intrauterine effect of prenatal smoking exposure on blood pressure in late adolescence.

Background— The widely reported inverse association between birth weight and risk of cardiovascular disease (CVD) has sparked theories about early life determinants of adult disease. Within-twin-pair analysis provides a unique opportunity to investigate whether factors shared within twin pairs influence the association. Methods and Results— In a population-based cohort of like-sexed twins with known zygosity born in Sweden from 1926 to 1958, disease-discordant twin pairs were identified through linkage to the National Inpatient and Cause of Death registers between 1973 and 2006. Co-twin–control analyses were performed on twins discordant for cardiovascular disease (n=3884), coronary heart disease (n=2668), and stroke (n=1372). Overall, inverse associations between birth weight and risk of cardiovascular diseases were seen within dizygotic but not monozygotic twin pairs. In dizygotic twins, the odds ratios for a 1-kg within-pair increase in birth weight were 0.74 (95% confidence interval, 0.56 to 0.98) for coronary heart disease and 0.57 (95% confidence interval, 0.37 to 0.88) for stroke. Conversely, no statistically significant associations were found within monozygotic twins (for coronary heart disease: odds ratio, 1.10; 95% confidence interval, 0.73 to 1.68; for stroke: odds ratio, 0.92; 95% confidence interval, 0.48 to 1.80). Conclusions— We found an association between birth weight and risk of cardiovascular disease within disease-discordant dizygotic but not monozygotic twin pairs. This indicates that the association between birth weight and cardiovascular disease could be a result of common causes, and that factors that vary within dizygotic but not monozygotic twin pairs may help identify them.

The relative importance of genetic and environmental factors for the occurrence of lower urinary tract symptoms (LUTS) is poorly understood.To (1) estimate the prevalence of urinary incontinence (UI), overactive bladder (OAB), and other LUTS and (2) to assess the heritability of these symptoms.Cross-sectional survey of LUTS in a national population-based cohort of Swedish twins 20-46 yr of age (n=42 582) from the Swedish Twin Registry.Prevalence rates were determined and heritability of LUTS (in female twins) was assessed using indicators of twin similarity.A total of 25 364 twins completed the questionnaire (response rate: 59.6%). LUTS were more common in women (UI: 7%; OAB: 9%; nocturia: 61%; micturition frequency: 18%) than in men (UI: 1%; OAB: 5%; nocturia: 40%; micturition frequency: 11%), and prevalence increased with age. The strongest genetic effects were observed for UI, frequency, and nocturia. The lowest estimate for genetic effects was observed for OAB where environmental effects dominated, and more specifically shared family environment accounted for a third or more of the total variation. For stress UI, a fifth of the total variation in susceptibility to the disorder could be attributed to shared environment. Nonshared environmental effects were seen in the range of 45-65% for the various LUTS. The prevalence of LUTS was low in the men, and there were too few male cases to compute measures of similarity or heritability estimates.This study provides robust evidence of a genetic influence for susceptibility to UI, frequency, and nocturia in women. In contrast, shared environmental factors seem more important for the predisposition to develop OAB, which may reflect familial patterns such as learning from parental behaviours.

Please cite this paper as: Tettamanti G, Altman D, Pedersen N, Bellocco R, Milsom I, Iliadou A. Effects of coffee and tea consumption on urinary incontinence in female twins. BJOG 2011;118:806–813. Objectives To assess the effect of coffee and tea consumption on symptoms of urinary incontinence. Design Population-based study. Setting The Swedish Twin Register. Population In 2005, all twins born between 1959 and 1985 in Sweden (n = 42 852) were invited to participate in a web-based survey to screen for common complex diseases and common exposures. The present study was limited to female twins with information about at least one urinary symptoms and coffee and tea consumption (n = 14 031). Main outcome measure The association between coffee and tea consumption and urinary incontinence, as well as nocturia, was estimated as odds ratios (ORs) with 95% confidence intervals. Results Women with a high coffee intake were at lower risk of any urinary incontinence (OR 0.78, 95% CI 0.64–0.98) compared with women not drinking coffee. Coffee intake and incontinence subtypes showed no significant associations whereas high tea consumption was specifically associated with a risk for overactive bladder (OR 1.34, 95% CI 11.07–1.67) and nocturia (OR 1.18, 95% CI 1.01–1.38). Results from co-twin control analysis suggested that the associations observed in logistic regression were mainly the result of familial effects. Conclusions This study suggests that coffee and tea consumption has a limited effect on urinary incontinence symptoms. Familial and genetic effects may have confounded the associations observed in previous studies.

LMO2 protein expression predicts survival in patients with rheumatoid arthritis and diffuse large B-cell lymphoma

Background In utero exposure to tobacco smoking has been suggested to cause persistent alterations in cognitive functioning. We examined if mothers’ smoking during pregnancy (SDP) is associated with long-term impairment in offspring stress coping and the causal mechanism behind a possible link. Methods We used a large cohort (n = 187 106) of young males in Sweden (mean age = 18.2 years), who underwent a semi-structured psychological assessment in 1997–2006, including an evaluation of stress coping ability, as part of the compulsory military conscript examination. We compared differentially exposed siblings within nuclear families and cousins in extended families and used multilevel structural equation models to disentangle genetic from environmental contributions to the association between SDP and stress coping. Results SDP and offspring stress coping was moderately strongly associated when comparing unrelated individuals [regression coefficient (b) = −0.38 on a nine-point scale; 95% confidence interval (CI) −0.40 to −0.36, P

Results In the cohort analyses, the risk of overweight was increased in sons of smoking mothers compared with sons of non-smokers: adjusted odds ratios 1.41, 95% confidence interval (CI) 1.34–1.49, and 1.56, 95% CI 1.46–1.66, for one to nine cigarettes per day, and 410 cigarettes per day, respectively. Stratifying for maternal smoking habits across two subsequent male pregnancies, there was an increased risk of overweight for the second son only if the mother was smoking in both male pregnancies. The effect of smoking during pregnancy on the offspring’s body mass index was not present when the association was evaluated within full and half sibling pairs. Conclusion The association between maternal smoking during pregnancy and offspring’s risk of overweight appears to be confounded by familial factors.

We examined the risk of tuberculosis in relation to birth weight and ponderal index among 21,596 Swedish twins born from 1926 through 1958. Using a cohort design, tuberculosis risk was 11% lower for every 500 g of birth weight (P = .05) and 8% lower for every 0.2 of ponderal index, calculated as birth weight in grams multiplied by 100 and divided by the cube of birth length in centimeters (P = .08). The association between birth weight and tuberculosis was stronger in male individuals than in female individuals. In co-twin control analyses among disease-discordant monozygotic twins, tuberculosis risk was 46% lower for every 500 g of birth weight (P = .05). The association was stronger in male individuals (87% risk reduction; P = .02) than it was in female individuals (16% reduction; P = .62). A similarly stronger relation with male sex, compared with female sex, was found for ponderal index. Because associations among monozygotic twins are largely independent of shared genetic or environmental factors, we postulate that fetal growth may play a causal role in susceptibility to tuberculosis, possibly through early programming of immunity.

Maternal smoking during pregnancy (SDP) is associated with lower academic achievement in offspring. The current study, which was based on all births in Sweden from 1983 through 1991, explored the possible causal processes underlying the association between SDP and offspring school grades and a standardized assessment of mathematic proficiency at age 15. The analyses compared relatives who varied in their exposure to SDP and who varied in their genetic relatedness. Although SDP was statistically associated with academic achievement when comparing unrelated individuals, the results suggest that SDP does not cause poorer academic performance, as full siblings differentially exposed to SDP did not differ in their academic scores. The pattern of results suggests that genetic factors shared by parents and their offspring explain significant variance in why offspring opposed to SDP have lower levels of academic achievement. Nevertheless, SDP impacts pregnancy-related outcomes. Reducing SDP, therefore, remains a major public health issue.

Summary Lundberg F, Cnattingius S, D'Onofrio B, Altman D, Lambe M, Hultman C, Iliadou A. Maternal smoking during pregnancy and intellectual performance in young adult Swedish male offspring. Paediatric and Perinatal Epidemiology 2010; 24: 79–87. Smoking during pregnancy has been linked to an increased risk of several adverse birth outcomes. Associations with deficits in cognitive development have also been suggested. It is unclear whether these associations are due to genetic and/or environmental confounding. In a population-based Swedish cohort study on 205 777 singleton males born to Nordic mothers between 1983 and 1988, we examined the association between maternal smoking during pregnancy and the risk of poor intellectual performance in young adult male offspring. In the cohort analyses, the risk of poor intellectual performance was increased in sons of smoking mothers compared with sons of non-smokers. Stratifying for maternal smoking habits across two pregnancies, there was an increased risk of poor intellectual performance for both sons if the mother was only smoking in the first pregnancy, but in neither son if the mother was only smoking in the second pregnancy. The effect of smoking during pregnancy on intellectual performance was not present when the association was evaluated within sibling pairs. Thus, the association between prenatal smoking exposure and offspring risk of low intellectual performance appears to be completely confounded by familial (genetic and early environmental) factors.

Objective To assess the impact of oral contraceptives on lower urinary tract dysfunction in premenopausal women. Design Nationwide cohort study. Setting National registry. Patient(s) A total of 10,791 women (born 1959–1985) from the population- based Swedish Twin Registry who participated in a web-based survey of common diseases. Intervention(s) None. Main Outcome Measure(s) Symptoms of urinary incontinence. Result(s) For users of oral contraception there was a significantly reduced risk for symptoms of stress urinary incontinence, mixed urinary incontinence, and urgency urinary incontinence. The reduction remained significant when adjusting for age, body mass index, and pregnancy history. A reduced prevalence of symptoms of overactive bladder in oral contraceptive users was also observed although the association was nonsignificant. There were no significant associations between lower urinary tract symptoms and women using a levonorgestrel-releasing intrauterine device compared with noncontraceptive users, with the exception of nocturia. Conclusion(s) Oral contraceptive use reduces the overall risk for symptoms of urinary incontinence.

Type-2 diabetes increases the risk of colorectal cancer, and is also associated with low birth weight. However, we found no evidence of associations between birth characteristics and risk of colorectal cancer (m=248) among Swedish twins.

Aims/hypothesis Evidence from candidate gene studies suggests that obesity may modify genetic susceptibility to type 2 diabetes and dyslipidaemia. On an aggregate level, gene–obesity interactions are expected to result in different heritability estimates at different obesity levels. However, this hypothesis has never been tested. Method The present study included 2,180 British female twins. BMI was used as an index of general obesity. Outcome measures were insulin sensitivity (indexed by quantitative insulin-sensitivity check index [QUICKI]) and fasting plasma lipid profile. Structural equation modelling was used to test whether BMI interacted with latent genetic and environmental effects to impact on the outcome measures. Results Genetic influences on triacylglycerol increased with BMI (p

We investigated whether infections with Parvovirus B19 and Herpes viruses in early pregnancy increase risks of second trimester miscarriage or delivery before 32 gestational weeks. Blood samples taken in early pregnancy were analyzed for Parvovirus B19 or Herpes viruses. Viremia was found in blood samples of 11 (4.7%) women with second trimester miscarriage and 10 (3.7%) women with very preterm birth, compared to 5 (1.7%) women who delivered at term, corresponding to adjusted odds ratios [95% CI] of 3.32 [0.93, 11.8] and 2.21 [0.71, 6.84], respectively. In stratified analyses, Parvovirus B19 viremia was associated with adjusted odds ratios of 3.76 [0.77, 18.3] for second trimester miscarriage and 2.66 [0.64, 11.1] for very preterm birth. Corresponding odds ratios for Human Herpes virus 6 viremia was 2.52 [0.33, 19.5] and 1.08 [0.14, 8.08], respectively. In conclusion, this study lends some support to the hypothesis that women with viremia in early pregnancy may face an increased risk of second trimester miscarriage or very preterm birth. Studies with larger sample sizes are needed.

Diffuse large B-cell lymphomas (DLBCL) can be subdivided into germinal centre (GC)-like and non-GC-like subtypes by CD10, BCL6 and MUM1/IRF4 status. We previously reported that patients with severe rheumatoid arthritis (RA) are at increased risk of non-GC DLBCL. This study examined a new GC-marker, human germinal-centre-associated lymphoma (HGAL) protein, in RA-DLBCL. Of 111, 38 (34%) DLBCL were HGAL-positive and showed less disseminated disease and a tendency toward improved overall survival compared to HGAL-negative cases. This supports that a majority of RA-DLBCL are of non-GC origin, indicating a specific role for activated peripheral B cells in the pathogenesis of RA-DLBCL.

The role of reproductive factors, such as parental age, in the pathogenesis of childhood leukemias is being intensively examined; the results of individual studies are controversial. This meta-analysis aims to quantitatively synthesize the published data on the association between parental age and risk of two major distinct childhood leukemia types in the offspring. Eligible studies were identified and pooled relative risk (RR) estimates were calculated using random-effects models, separately for childhood acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML). Subgroup analyses were performed by study design, geographical region, adjustment factors; sensitivity analyses and meta-regression analyses were also undertaken. 77 studies (69 case-control and eight cohort) were deemed eligible. Older maternal and paternal age were associated with increased risk for childhood ALL (pooled RR = 1.05, 95 % CI 1.01-1.10; pooled RR = 1.04, 95 % CI 1.00-1.08, per 5 year increments, respectively). The association between maternal age and risk of childhood AML showed a U-shaped pattern, with symmetrically associated increased risk in the oldest (pooled RR = 1.23, 95 % CI 1.06-1.43) and the youngest (pooled RR = 1.23, 95 % CI 1.07-1.40) extremes. Lastly, only younger fathers were at increased risk of having a child with AML (pooled RR = 1.28, 95 % CI 1.04-1.59). In conclusion, maternal and paternal age represents a meaningful risk factor for childhood leukemia, albeit of different effect size by leukemia subtype. Genetic and socio-economic factors may underlie the observed associations. Well-adjusted studies, scheduled by large consortia, are anticipated to satisfactorily address methodological issues, whereas the potential underlying genetic mechanisms should be elucidated by basic research studies.

Background: The red cell indices quantify the size, number and oxygen-carrying ability of erythrocytes. Although the genetic basis of many monogenic forms of anaemia is well understood, comparatively little is known about the genes responsible for variation in the red cell indices among healthy participants. Objective: To identify quantitative trait loci (QTLs) responsible for normal variation in the red cell indices of 391 pairs of dizygotic twins who were measured longitudinally at 12, 14 and 16 years of age. Results: Evidence suggesting linkage of red cell indices to haemoglobin concentration (LOD = 3.03) and haematocrit (LOD = 2.95) on chromosome 6q23, a region previously identified as possibly harbouring a QTL for haematocrit, was found. Evidence for linkage to several other regions of the genome, including chromosome 4q32 for red cell count and 7q for mean cell volume, was also found. In contrast, there was little evidence of linkage to the chromosomal regions containing the genes for erythropoietin (7q21) and its receptor (19p13.2), nor to the regions containing the genes for the haemoglobin α (16p13.3) and β chains (11p15.5). Conclusion: Findings provide additional evidence for a QTL affecting haemoglobin and haematocrit on chromosome 6q23. In contrast, polymorphisms in the genes coding for erythropoietin, its receptor and the haemoglobin α and β chains do not appear to contribute substantially to variation in the red cell indices between healthy persons.

Chronic inflammatory conditions such as rheumatoid arthritis (RA) have been associated with malignant lymphomas. This study was undertaken to investigate which patients are at highest risk, and whether antirheumatic treatment is hazardous or protective.We performed a matched case-control study of 378 consecutive Swedish RA patients in whom malignant lymphoma occurred between 1964 and 1995 (from a population-based RA cohort of 74,651 RA patients), and 378 controls. Information on disease characteristics and treatment from onset of RA until lymphoma diagnosis was abstracted from medical records. Lymphoma specimens were reclassified and tested for Epstein-Barr virus (EBV). Relative risks (odds ratios [ORs]) for lymphomas (by subtype) associated with deciles of cumulative disease activity were assessed, as were ORs associated with drug treatments.The relative risks of lymphoma were only modestly elevated up to the seventh decile of cumulative disease activity. Thereafter, the relative risk increased dramatically (OR ninth decile 9.4 [95% confidence interval 3.1-28.0], OR tenth decile 61.6 [95% confidence interval 21.0-181.0]). Most lymphomas (48%) were of the diffuse large B cell type, but other lymphoma subtypes also displayed an association with cumulative disease activity. Standard nonbiologic treatments did not increase lymphoma risk. EBV was present in 12% of lymphomas.Risk of lymphoma is substantially increased in a subset of patients with RA, those with very severe disease. High inflammatory activity, rather than its treatment, is a major risk determinant.

Patients with rheumatoid arthritis (RA) are at increased risk of malignant lymphomas, with a correlation between RA disease severity and lymphoma risk, most pronounced for diffuse large B cell lymphomas (DLBCLs), which also constitute the majority of RA-associated lymphomas. DLBCLs can be further subdivided into germinal center (GC)-like and non-GC-like subtypes, with different cellular origins and prognoses. This study was undertaken to investigate whether RA displays a specific association with any of the DLBCL subtypes.We identified 139 patients with DLBCLs within a population-based case-control study of 378 RA patients with lymphoma. The DLBCLs were examined for CD10, Bcl-6, and interferon regulatory factor 4 expression patterns, subclassified into GC and non-GC subtypes, and then correlated with clinical parameters.We found a statistically significant predominance of the non-GC subtype (97 patients; 70% of all DLBCLs). These patients more often had an advanced stage of lymphoma at diagnosis and had a worse 5-year overall survival rate (16% versus 33%) compared with patients with the GC subtype. There was a strong association with RA disease activity in both subtypes, with70% of the GC and non-GC cases occurring in RA patients with the highest overall disease activity scores.These findings suggest that severe RA is particularly associated with the non-GC subtype of DLBCL, and indicate a critical role of activated peripheral B cells as the cells of origin in these lymphomas.

Twin studies of lipids have almost exclusively involved Caucasians. People of African descent are known to show a healthier lipid profile, but relatively little is known about ethnic differences in genetic and environmental influences on lipids. One hundred and six African American (AA) and 106 European American (EA) twins (30 singletons and 91 complete pairs: 49 monozygotic, 21 dizygotic and 21 opposite-sex) from the south-eastern United States were studied (mean age 17.9 ± 3.2 years; 79% fasting). Lipids were assayed with the Cholestech LDX system. Analyses were adjusted for fasting status. Generalized estimating equations were used to test for the effects of sex and ethnicity on means, controlling for the dependence within twin pairs. Structural equation modeling was used to estimate genetic and environmental effects on each lipid variable. Females showed higher high-density lipoprotein (HDL) values than males (p< .001) and AAs showed higher HDL values than EAs (p< .001). EA males had higher triglyceride values than other groups (p= .02). All parameter estimates could be set equal across sex. Parameter estimates for total cholesterol, triglycerides and HDL could be set equal across ethnicity. The best fitting model for low- density lipoprotein (LDL) showed higher heritability in AAs (.92) than EAs (.69). Heritabilities ranged from 69% to 92%, with remaining variation explained by nonshared environmental effects. Adjustment for body mass index had virtually no effect on the heritability estimates. In this first twin study on lipids to include AAs, no ethnic differences in heritability were found except for LDL, where AAs exhibited higher estimates.

The aim of the current study was to investigate the importance of genetic and environmental effects in the variation of body mass index, and to investigate linkage for obesity to previously reported candidate regions on chromosome 2 and 10. A sample of 1422 twin pairs from the population based Swedish Twin Registry was used in order to estimate the genetic and environmental effects in the variation of body mass index by means of structural equation modeling. A selection of those, 51 concordant and 155 discordant for obesity, was used for the linkage analysis by implementing the "combined" Haseman-Elston approach. Heritability of body mass index ranged from 59-70%, implying that genetic effects were of importance for the variation of obesity, and there were significant sex and age differences. Linkage could not be verified in candidate regions of chromosomes 2 and 10, indicating that these genetic variants have a significant effect in extreme obese populations rather than in moderately obese Caucasians. However, the results were sensitive to issues related to power, minor effects of the genes, ethnic differences and the complex mechanism underlying obesity.

The importance of genetic factors for the susceptibility to disease has been widely recognized in the last years. Genes have been identified for monogenic diseases and the challenge lying ahead is the identification of genetic components of importance and the environments in which they are expressed for complex diseases, that is, multiple genetic factors act and interact with each other or environmental factors to add to the complexity. This paper gives a brief overview of some genetic epidemiological approaches, concepts and recent methodological developments related to the study of risk factors for cardiovascular disease in twin and family studies.

Importance Several recent population-based studies have linked exposure to maternal smoking during pregnancy to increased risk of severe mental illness in offspring (eg, bipolar disorder, schizophrenia). It is not yet clear, however, whether this association results from causal teratogenic effects or from confounding influences shared by smoking and severe mental illness. Objective To examine the association between smoking during pregnancy and severe mental illness in offspring, adjusting for measured covariates and unmeasured confounding using family-based designs. Design, Setting, and Participants This study analyzed population register data through December 31, 2013, for a cohort of 1 680 219 individuals born in Sweden from January 1, 1983, to December 31, 2001. Associations between smoking during pregnancy and severe mental illness in offspring were estimated with adjustment for measured covariates. Cousins and siblings who were discordant on smoking during pregnancy and severe mental illness were then compared, which helped to account for unmeasured genetic and environmental confounding by design. Exposures Maternal self-reported smoking during pregnancy, obtained from antenatal visits. Main Outcomes and Measures Severe mental illness, with clinical diagnosis obtained from inpatient and outpatient visits and defined using International Classification of Diseases codes for bipolar disorder and schizophrenia spectrum disorders. Results Of the 1 680 219 offspring included in the analysis, 816 775 (48.61%) were female. At the population level, offspring exposed to moderate and high levels of smoking during pregnancy had greater severe mental illness rates than did unexposed offspring (moderate smoking during pregnancy: hazard ratio [HR], 1.25; 95% CI, 1.19-1.30; high smoking during pregnancy: HR, 1.51; 95% CI, 1.44-1.59). These associations decreased in strength with increasing statistical and methodologic controls for familial confounding. In sibling comparisons with within-family covariates, associations were substantially weaker and nonsignificant (moderate smoking during pregnancy: HR, 1.09; 95% CI, 0.94-1.26; high smoking during pregnancy: HR, 1.14; 95% CI, 0.96-1.35). The pattern of associations was consistent across subsets of severe mental illness disorders and was supported by further sensitivity analyses. Conclusions and Relevance This population- and family-based study failed to find support for a causal effect of smoking during pregnancy on risk of severe mental illness in offspring. Rather, these results suggest that much of the observed population-level association can be explained by measured and unmeasured factors shared by siblings.

Hereditary factors may be involved in the pathogenesis of type 2 diabetes. A polymorphism in the hormone-sensitive lipase (HSL) gene (HSLi6) is associated with obesity and diabetes, although it is unknown whether the polymorphism is functional and thereby influences lipolysis. We genotyped 355 apparently healthy nonobese male and female subjects for the HSLi6 polymorphism. Allele 5 was found to be the most common allele (allele frequency 0.57). In 117 of the subjects, we measured abdominal subcutaneous fat cell lipolysis induced by drugs acting at various steps in the lipolytic cascade. The lipolysis rate induced by norepinephrine isoprenaline (acting on β-adrenoceptors), forskolin (acting on adenylyl cyclase), and dibutyryl cyclic AMP (acting on HSL) were all decreased by ∼50% in allele 5 homozygotes, as compared with noncarriers. Heterozygotes showed an intermediate lipolytic rate. The difference in lipolysis rate between genotypes was more pronounced in men than in women. We conclude that allele 5 of the HSLi6 polymorphism is associated with a marked decrease in the lipolytic rate of abdominal fat cells. This may in turn contribute to the development of obesity.

A rare β2-adrenoceptor gene polymorphism, Thr164Ile, has been described that impairs receptor function when transfected into cell lines. We investigated whether the polymorphism influences native receptor function by studying lipolysis in freshly isolated subcutaneous fat cells from 236 apparently healthy subjects. Twelve subjects were heterozygous for the 164Ile variant. The fat cells of Ile carriers displayed a 6 fold increase (P=0.02) in the lipolytic EC50 of terbutaline (a selective β2-adrenoceptor agonist), but no change in the lipolytic action of dobutamine (a selective β1-adrenoceptor agonist), compared with the Thr carriers. Maximum adrenoceptor agonist stimulated lipolysis did not differ between Thr and Ile carriers. The influence of two other polymorphisms (Arg16Gly and Gln27Glu) in the β2-adrenoceptor gene was considered. Six 164Ile carriers also carried the 16Gly and 27Glu alleles. The latter combination occurred among 105 of the 164Thr carriers. For the 16Gly27Glu subgroup, the EC50 of terbutaline was about 10 fold higher in 164Ile as than in 164Thr carriers (P=0.02) but there was no difference between genotypes in maximum terbutaline action. There was no difference between groups in dobutamine action. In conclusion, the 164Ile variant of the β2-adrenoceptor is associated with a decreased native adipocyte receptor function, as evidenced by a marked increase in the half maximal effective concentration of the lipolytic action of a selective β2-adrenoceptor agonist. This suggests that genetic variance in the β2-adrenoceptor gene might be important for catecholamine function in humans, at least as far as adipocyte lipolysis is concerned. British Journal of Pharmacology (2001) 133, 708–712; doi:10.1038/sj.bjp.0704125

The contribution of genetic and environmental factors to variation in lipids and apolipoproteins has been estimated in previous twin and family studies. However, it is unclear whether there are sex and/or age differences in parameter estimates. We investigated a sample selected from the population-based Swedish Twin Registry of 725 like- and unlike-sex twin pairs, ages 17-85. Quantitative genetic methods were used to evaluate sex and age differences in genetic and environmental variation in lipid and apolipoprotein levels in three age groups, 17-49, 50-69, and 70-85. Heritabilities for lipids and apolipoproteins ranged from 35%-74%. Consistent sex differences were found in triglycerides. Females had higher heritabilities (56%) than males (35%) across the age groups. Total phenotypic variation increased across the age groups for cholesterol and apolipoprotein B due to an increase in unique environmental variance components. In contrast, in apolipoprotein A1 variance was highest in the middle age group and no differences were found in the phenotypic variance between age groups for triglycerides. We concluded that differences in phenotypic variation for cholesterol and apolipoprotein B were almost entirely due to the accumulation of environmental experiences throughout life, whereas there were no consistent patterns of differences in phenotypic variance for apolipoprotein A1 and triglycerides.

Most, but not all, studies report a positive association between birth weight, as an indirect marker of prenatal hormone exposure, and offspring breast cancer risk, particularly premenopausal breast cancer. Females from opposite-sexed twin pairs may also be prenatally exposed to androgens from their twin brothers. A Swedish study of opposite-sexed twins with a small sample size found a very strong positive association between female birth weight and breast cancer risk. In this case-control study, nested within a cohort of female opposite-sexed twins, we included 543 breast cancer case subjects diagnosed in the period from 1972 to 2008 and 2715 matched control subjects. Conditional logistic regression estimated the breast cancer risk associated with birth weight and other birth characteristics, including gestational age and co-twin birth weight. All statistical tests were two-sided. There was no association between birth weight (odds ratio = 1.01; 95% confidence interval = 0.70 to 1.46) or twin brother's birth weight and risk of breast cancer, which suggests the previously reported strong positive association may have been a chance finding.

Methods: In 2005, a total of 14,094 female twins born 1959–1985 who had been included in the Swedish Twin Registry participated in a survey on common exposures and complex diseases, including urinary incontinence. Information regarding birth weight and gestational age was obtained from the Medical Birth Register (for twins born 1973–1985) and from the medical archives (for twins born 1959–1972). A logistic regression model based on generalized estimating equations was used to estimate odds ratios (ORs) with 95 % confidence intervals (CIs).Results: In both crude and adjusted analysis, birth weight and SGA had no effect on UI. An interaction between low birth weight (

Abstract —Plasma fibrinogen is a major risk factor for coronary heart disease, stroke, and peripheral artery disease. There is evidence that genetic variation in the β-fibrinogen gene contributes to the rate of synthesis of fibrinogen, but the molecular mechanism underlying the genetic heritability of the plasma fibrinogen concentration is largely unknown. We evaluated the physiological roles of 5 common nucleotide substitutions in the promoter region of the β-fibrinogen gene at positions −148, −249, −455, −854, and −993 from the transcriptional start site. Electrophoretic mobility shift assays revealed distinct differences in the binding characteristics of nuclear proteins between wild-type and mutant fragments of both the −455G/A and −854G/A polymorphisms, whereas no clear differences were observed for the −148C/T, −249C/T, and −993C/T sites. Transfection studies in HepG2 cells showed increased basal rates of transcription for both the G-to-A substitution at position −455 (+50%, P P

OBJECTIVE—To determine the diabetes- and obesity-related risks for surgically managed stress urinary incontinence and pelvic organ prolapse. RESEARCH DESIGN AND METHODS—This twin cohort study used the Swedish Twin Register to identify 8,443 female twin pairs born from 1926 through 1958. The association between diabetes and pelvic floor surgery was estimated while taking into account the correlated (twin) structure of the data. RESULTS—For type 1 and type 2 diabetes, no significant associations were observed for stress urinary incontinence (odds ratio [OR] 1.0 [95% CI 0.1–9.2] and 2.0 [1.0–4.0], respectively). There were no cases of prolapse surgery in type 1 diabetic subjects, and for type 2 diabetes the risk estimate was nonsignificant (1.6 [1.0–2.7]). BMI >25 kg/m2, age ≥60 years, and childbirth were the strongest risk factors for having incontinence surgery. CONCLUSIONS—Our data suggest that diabetes is not associated with stress urinary incontinence or pelvic organ prolapse surgery.