Objective: To examine the association between leisure time physical activity over a three year period and health related behaviour, social relationships, and health status in late adolescence as part of a nationwide longitudinal study. Methods: Five birth cohorts of adolescent twins aged 16 at baseline (n = 5028; 2311 boys and 2717 girls) participated in the study. Questionnaires on leisure time physical activity, other health related behaviour, social relationships, and health status were sent to the twins on their 16th and 17th birthdays and six months after their 18th birthday. The combined response rate to the three questionnaires was 75.8% for boys and 81.7% for girls. Those who answered in all three questionnaires that their frequency of physical activity was 4-5 times a week or more were defined as persistent exercisers, and those who exercised at most twice a month in all three were defined as persistently inactive. Logistic regression analyses were used to identify baseline variables associated with outcome measures. Results: Overall, 20.4% of boys and 13.0% of girls were persistent exercisers and 6.5% of boys and 5.3% of girls were persistently inactive. In both sexes, smoking, irregular breakfast eating, attending vocational school, and poor self perceived current health were significantly associated with persistent inactivity. Conclusions: Persistent physical inactivity in adolescents is associated with a less healthy lifestyle, worse educational progression, and poor self perceived health. Tailoring methods to promote physical activity may prove useful for influencing other health habits. Such programmes are indicated for vocational schools in particular.

We studied the inheritance of migraine and concomitant symptoms among 2690 monozygotic (1524 female and 1166 male) pairs and 5497 dizygotic (2951 female and 2546 male) twin pairs. Our material consists of a population-based questionnaire study among Finnish twins in 1981. The definition of migraine is based on a questionnaire method. Concordance was assessed using probandwise concordance rates and tetrachoric correlations for monozygotic (MZ) and dizygotic (DZ) twin pairs. For estimating the contribution of genetic factors to the susceptibility of migraine, a polygenic multifactorial model was used. Structural equation models were applied for estimating variance components and to compare different genetic models. Nearly one-half (40% to 50%) of the liability to migraine is attributable to genetic factors. In all structural analyses, the model with both additive genetic and unshared environmental component had the best goodness-of-fit value. The genetic component varied between 34% to 51% in different migraine types. There were no remarkable differences between sexes except in the effects due to dominance, where the proportion was 26% for men and 14% for women. Concomitant symptoms among subjects within pairs concordant for headache had genetic effects varying from 56% (subjects with unilaterality) and 56% (subjects with visual symptoms) to 45% (persons with nausea and vomiting). The two threshold model of headache points to the continuum model of headache, and the thresholds represent different levels of severity of the pain. Our results emphasize a multifactorial and higher than previously reported genetic pattern in the etiology of migraine. Also unshared environmental factors play an important role.

OBJECTIVE: 1) To estimate the heritability of body mass index (BMI) in twins aged 16 y and 17 y, with a special emphasis on gender-speci®c genetic effects and 2) to compare heights, weights, BMIs, and prevalences of`overweight' (BMI ! ! 25 kgam 2 ) in these twins and in singletons aged 16.5 y. DESIGN: Cross-sectional and longitudinal epidemiological questionnaire study of twins at ages 16 y and 17 y, and cross-sectional study of singletons at age 16.5 y. MEASUREMENTS: BMI (kgam 2 ) was calculated from self-reported heights (m) and weights (kg). SUBJECTS: 4884 twins (2299 boys, 2585 girls) at baseline (age 16 y), 4401 twins (2002 boys, 2399 girls) at age 17 y, and 2509 singletons (1147 boys, 1362 girls) at age 16.5 y. Both twin and singleton samples are nationally representative. RESULTS: At the ages of 16 y and 17 y, genetic effects accounted for over 80% of the interindividual variation of BMI. The correlations for male ± female pairs were smaller than for either male-male or female ± female dizygotic pairs. The singletons, especially the boys, had a higher BMI than the twins. Nine percent of singleton boys, but only 4 ± 6% of twin boys and twin and singleton girls were`overweight' (BMI ! ! 25 kgam 2 ). CONCLUSIONS: Among adolescents, genetic factors play a signi®cant role in the causes of variation in BMI. The genetic modelling suggested that the sets of genes explaining the variation of BMI may differ in males and females. At this age, the twin boys, but not girls, seem to be leaner than singletons. Further follow-up will indicate whether these small differences disappear, and if not, what implications it might have to the generalizability of twin studies.

Participation in physical activity during childhood and adolescence is frequently mentioned as one factor likely to promote a more active lifestyle in adulthood with its health benefits. We studied the changes in leisure-time physical activity pattern and self-reported fitness during a three-year period in adolescence and investigated whether the type of sports has an effect on stability of physical activity at leisure. A questionnaire with identical physical activity items was sent to Finnish twins on their 16th and 17th birthdays and 6 months after the 18th birthday. A total of 1338 boys and 1596 girls responded to all three questionnaires, with response rates of 73.6% and 86.5%. The proportions of very active adolescents and adolescents with very good self-reported fitness seem to be alike at each age. Among girls, 23.7% to 27.7% reported being very active (4-5 times a week) and 13.7% to 15.1% considered their physical fitness to be very good at the ages of 16, 17 and 18. Among boys, the comparable percentages were 31.5% to 35.5% and 30.6% to 34.4%. However, the longitudinal three-year follow up showed substantial changes over time among individuals from one physical activity group to another. Only 19.1% of boys and 11.2% of girls were persistent exercisers (i.e., very active on all three years) and 15.6% of boys and 5.1% of girls were persistently fit (i.e., very good self-reported fitness on all three years). Stability of leisure-time physical activity was highest among those who participated in several different types of sports. Among boys the proportion of persistent exercisers was highest for those who participated in cross-country skiing, jogging and body-building (22.0-41.5%) and among girls for those who participated in ball games (11.9-28.6%). Those who participated in organised sports were more often persistent exercisers than those who did not (odds ratio = 13.2 for boys (CI 9.4-18.7) and 8.9 for girls (CI 6.4-12.5)). Also, those who participated in organised sports were more often persistently fit (odds ratio = 7.3 for boys (CI 5.2-10.2) and 10.4 for girls (CI 6.4-16.9). Adolescents are recommended to participate in and try different types of sports, and especially for girls ball games would appear to favour long-term maintenance of leisure-time physical activity.

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Background-Previous studies have suggested that, in addition to genetic liability and environment in early childhood, intrauterine life also influences the risk for asthma beyond childhood. Low birth weight, prematurity, young maternal age, and maternal smoking have all shown an association with asthma. The eVect of perinatal factors on the risk for asthma in relation to familial and social risk factors was studied in a nationwide population-based sample of adolescent twins. In addition to a distribution of birth characteristics among twins which diVers from that of singletons, data on twins enable a distinction to be made between genetic and environmental sources of variation. Methods-Questionnaires were sent to five consecutive birth cohorts of Finnish 16 year old twins born in 1975-9 and to their parents (3065 families). The outcome measure was life time prevalence of doctor-diagnosed asthma in these adolescents. The association between asthma and potential risk factors was assessed by multiple logistic regression and discordant twin pair analysis. Results-Risk for asthma increased with increasing ponderal index (p for trend <0.01) and decreasing maternal age (p for trend <0.05). Among the 25% of twins with the highest ponderal index, the odds ratio for asthma was 1.82 (95% confidence interval 1.18 to 2.79) compared with those in the lowest 25%. Neither birth weight, gestational age, nor Apgar score was associated with asthma. When perinatal risk factors were combined with familial and social risk factors, ponderal index, maternal smoking, parental asthma, and sibship size were all significant independent determinants of asthma in these adolescents. Conclusions-The risk for asthma in adolescent twins increases with increasing ponderal index when adjusted for familial and social factors. (Thorax 2000;55:25-31)

Studies of parental influence on children's physical activity have had different results. Parental effect on physical activity during adolescence is less studied, and three generation studies have not been carried out. The purpose of our study was to examine intra- and intergenerational associations of leisure time physical activity among family members in three generations. Due to the major changes in society during this time, we also took into consideration the socioeconomic status of the adult subjects. The material consisted of 3254 twins at the age of 16, their parents and grandparents. Twins and their parents received a questionnaire in 1991-1993, which included questions about the health and lifestyle, socioeconomic status and leisure time physical activity. The parents' questionnaire also included questions about their own parents' leisure time physical activity and socioeconomic status. Based on these questions adolescents, parents and grandparents were classified into physical activity classes. The socioeconomic classification of parents and grandparents was based on their occupation. Intragenerational physical activity patterns were significantly associated with each other. Among adolescents the strongest correlation were between monozygotic boys (0.720) and monozygotic girls (0.638). Physical activity patterns were not associated between generations, but there was a significant difference between very active and inactive mothers concerning their daughters' physical activity. Farmers had the lowest proportion of very active subjects only among the parental generation. Because physical activity patterns do not appear to be transmitted from one generation to the next, it is probable that by constant training and education we can obtain the benefits of physical activity.

Background Adolescent alcohol abuse is associated with adverse outcomes in early adulthood, but differences in familial status and structure and household and community environments correlate with both adolescent drinking and adverse adult outcomes and may explain their association. We studied drinking-discordant twin pairs to evaluate such confounds to ask: Will between-family associations replicate in within-family comparisons? Methods With longitudinal data from > 3,000 Finnish twins, we associated drinking problems at age 18½ with 13 outcomes assessed at age 25; included were sustained substance abuse, poor health, physical symptoms, early coital debut, multiple sexual partners, life dissatisfaction, truncated education, and financial problems. We assessed associations among twins as individuals with linear regression adjusted for correlated observations; within-family analyses of discordant twin pairs followed, comparing paired means for adult outcomes among co-twins discordant for adolescent problem drinking. Defining discordance by extreme scores on self-reported problem drinking at age 18½ permitted parallel analyses of twins as individuals and discordant twin pairs. Alternate definitions of pair-wise discordance and difference score correlations across the entire twin sample yielded supplementary analyses. Results All individual associations were highly significant for all definitions of discordance we employed. Depending on definitions of discordance, 11 to 13 comparisons of all drinking-discordant twin pairs and 3 to 6 comparisons of discordant monozygotic twin pairs replicated between-family associations. For most outcomes, effect size attenuated from individual level analysis to that within discordant MZ twin pairs providing evidence of partial confounding in associations reported in earlier research. The exception was the General Health Questionnaire; at age 25, GHQ-12 had equivalent associations with age 18½ RAPI across all comparisons. Conclusions Our analyses control for shared family background, and, partly or fully, for shared genes, to yield within-family replications and more compelling evidence than previously available that adolescent alcohol abuse disrupts transitions into early adulthood.