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Background. This study examined the role of genetic and environmental factors explaining individual differences in women's walking ability in old age. Methods. A maximal walking speed test over 10 meters and a 6-minute walking endurance test were done under standard conditions among 92 monozygotic and 105 dizygotic pairs of twin sisters reared together, aged 63-75 years. Results. The mean maximum walking speed was 1.73 [+ or -] 0.32 m/s and the mean distance covered in the 6-minute walking test was 525.6 [+ or -] 77.3 m. Multivariate genetic modeling showed that a minor part of the variances in walking speed (16%, 95% confidence interval [CI]: 0%-54%) and endurance (20%, 95% CI: 0%-56%) were accounted for by genetic influences, and that the genetic influences were common to both traits. The corresponding proportions for common environmental factors were 37% (95% CI: 4%-58%) and 26% (95% CI: 0%-52%), and for individual environmental factors 46% (95% CI: 35%-59%) and 54% (95% CI 42%-68%), respectively. The environmental effects were partially common to both traits. Conclusions. Among relatively healthy older women, a modest portion of the variances of walking speed and endurance were accounted for by genetic factors, whereas shared and individual environmental factors explained most of the variance in both traits.

Migration is often undertaken to improve living conditions and to increase access to welfare resources. This study aims to analyse to what extent migration from Finland to Sweden has influenced [...]

Background. Among older people, distraction while walking may increase the risk of falls. Factors underlying individual differences in dual tasking are not fully understood. Our aim was to study the effect of a second task on maximal walking speed and to examine whether individual differences in walking speed measured with and without a second task are accounted for by genetic and environmental influences shared across tasks or specific to each task. Methods. The data were collected from the 101 monozygotic and 116 dizygotic twin pairs aged 63-76 years recruited from the Finnish Twin Cohort. Maximal walking speed (MWS) over 10 m was measured on a laboratory corridor and timed with photocells. The test was repeated while subjects performed, first, a manual task (MWSmanual) and, second, a verbal task (MWSverbal). Results. Mean walking speed without a simultaneous task was 1.72 m/s (standard deviation [SD] 0.33), with a manual task it was 1.52 m/s (SD 0.26), and with a verbal task it was 1.36 m/s (SD 0.27). Multivariate genetic analysis showed that an additive genetic factor in common accounted for 17% of individual differences in MWS, 19% in MWSmanual, and 12% in MWSverbal. In addition, MWSverbal had a genetic factor specific to it accounting for 10% of the variance. Shared environmental influences, common to all three traits, accounted for 39%, 27%, and 21% of the individual differences, respectively. Conclusion. Approximately half of the individual differences in walking with or without another task were accounted for by genetic and nongenetic familial effects in common, and the rest of the variation was accounted for by unique environmental factors in common and factors specific to walking tests.

Objective. To examine the association of teacher- and parent-rated behavior with headache in a prospective follow-up study of adolescent Finnish twins. Methods. Questionnaire data were collected during 1995-2001 from a nationwide sample of Finnish families of U-year-old twins who were born 1983-1987 (n = 5393) and again at age of 14. Psychological factors were measured by using parents' and teachers' ratings of a 37-item multidimensional rating instrument at the ages of 11 and 14. Results. At age 11, headache frequency (5 categories) was associated with total scales of externalizing and internalizing problem behaviors and adaptive behaviors, assessed by parents, but only with externalizing problem behaviors assessed by teachers. Results were similar at age 14. The incidence of at least monthly headache between the ages of 11 and 14 years was predicted by externalizing problem behaviors and 2 subscales of adaptive behaviors: constructiveness and poor compliance. In twin pairs discordant for headache, externalizing and internalizing problem behaviors were more common among headache sufferers than among headache-nonsufferers. Headache-discordant monozygotic co-twins confirmed the association of externalizing problem behaviors with headache. Conclusions. The frequency of adolescents' headache is predicted by psychological factors, especially by externalizing problem behaviors. This seems to be independent of genetic or familial influences on behavior and headache. Behavioral problems may be a sign of worsening of headache or vice versa., ABBREVIATIONS. MPNI, Multidimensional Peer Nomination Inventory; MZ, monozygotic; DZ, dizygotic; Tr-MPNI, Teacher Rating Form; Pr-MPNI, Parent Rating Form; OR, odds ratios; CI, confidence interval; CBCL, Child Behavior Checklist. Headache is [...]

Examples of gene-environment interaction in human behavioral data are relatively rare; those that exist have used simple, dichotomous measures of the environment. The authors describe a model that allows for the specification of more continuous, more realistic variations in environments as moderators of genetic and environmental influences on behavior. Using data from a population-based Finnish twin study, the authors document strong moderating effects of socioregional environments on genetic and environmental influences on adolescent alcohol use, with nearly a five-fold difference in the magnitude of genetic effects between environmental extremes. The incorporation of specific environmental measures into genetically informative designs should prove to be a powerful method for better understanding the nature of gene-environment interaction and its contribution to the etiology of behavioral variation.

Most cancer probably have an environmental cause rather than a genetic cause. This was the conclusion of researchers who analyzed cancer rates in 44,788 pairs of twins in Swedish, Finnish, and Danish twin registries. The strongest hereditary component occurred in stomach, colorectal, lung, breast, and prostate cancer. Nevertheless, heredity only accounted for about 42% of the risk of prostate cancer, 35% of the risk of colorectal cancer, and 27% of the risk of breast cancer.

Physical activity may lead to lower mortality rates. An analysis of death rates among approximately 16,000 men and women participating in the Finnish Twin study. Between 1977 and 1994, 1,253 people died. Those who exercised at least 6 times a month for 30 minutes had about half the death rate of those who never exercised at all. This was true even among 434 pairs of twins, one of whom had died. This indicates that genetic factors are not responsible for the reduced death rate seen in other groups who exercise on a regular basis., Context. -- Physical activity and fitness are believed to reduce premature mortality, but whether genetic factors modify this effect is not known. Objective. -- To investigate leisure physical activity and mortality with respect to familial aggregation of health habits during childhood and factors that may enable some individuals to achieve higher levels of fitness. Design. -- Prospective twin cohort study. Setting. -- Finland. Subjects. -- In 1975, at baseline, 7925 healthy men and 7977 healthy women of the Finnish Twin Cohort aged 25 to 64 years who responded to a questionnaire on physical activity habits and known predictors of mortality. Those who reported exercising at least 6 times per month with an intensity corresponding to at least vigorous walking for a mean duration of 30 minutes were classified as conditioning exercisers, those who reported no leisure physical activity were classified as sedentary, and other subjects were classified as occasional exercisers. Main Outcome Measures. -- All-cause mortality and discordant deaths among same-sex twin pairs from 1977 through 1994. Results. -- Among the entire cohort, 1253 subjects died. The hazard ratio for death adjusted for age and sex was 0.71 (95% confidence interval [CI], 0.62-0.81) in occasional exercisers and 0.57 (95% CI, 0.45-0.74) in conditioning exercisers, compared with those who were sedentary (P for trend [is less than] .001). Among the twin pairs who were healthy at baseline and discordant for death (n=434), the odds ratio for death was 0.66 (95% CI, 0.46-0.94) in occasional exercisers and 0.44 (95% CI, 0.23-0.83) in conditioning exercisers compared with those who were sedentary (P for trend, .005). The beneficial effect of physical activity remained after controlling for other predictors of mortality. Conclusion. -- Leisure-time physical activity is associated with reduced mortality, even after genetic and other familial factors are taken into account. JAMA. 1998;279:440-444