BACKGROUND: The prevalence of asthma is rising and there are recent reports of increasing asthma rates among top level skiers and runners in the Nordic countries. METHODS: The lifetime occurrence of pulmonary diseases (asthma, chronic bronchitis, emphysema) and current bronchitis symptoms was compared in former elite male athletes (n = 1282) who represented Finland between 1920 and 1965 at least once in international competitions and controls (n = 777) who, at the age of 20, were classified as healthy and who responded to a questionnaire in 1985. The presence of disease and symptoms was identified from the questionnaire and, in the case of asthma, also from a nationwide reimbursable medication register. The death certificates of the subjects of our original cohort who died between 1936 and 1985 were also investigated to determine the cause of death. RESULTS: The occurrence of the pulmonary diseases was associated with age, smoking habits, occupational group, and a history of exposure to chemicals. After adjusting for these variables, athletes who participated in mixed sports (odds ratio (OR) 0.46, 95% confidence interval (CI) 0.23 to 0.92) and power sports (OR 0.43, 95% CI 0.21 to 0.87) had lower odds ratios for emphysema, and endurance sports athletes had a lower odds ratio for the presence of at least one pulmonary disease (OR 0.53, 95% CI 0.28 to 0.98) when compared with controls. Athletes also tended to have fewer reimbursable medications for asthma and fewer current symptoms for chronic bronchitis. Between 1936 and 1985 two controls but none of the athletes died of asthma. CONCLUSIONS: The lifetime occurrence of asthma or other pulmonary diseases is not increased in former elite athletes, and exercise alone, even in a cold environment, did not appear to increase the prevalence of asthma, at least up to the mid 1980s.
A cohort of 2269 male world class athletes from the years 1920-65 was followed up through the Finnish Cancer Registry for cancer incidence during 1967-95. There were 331 cases of cancer while the expected number based on the national cancer incidence rates was 404; the standardized incidence ratio (SIR) was 0.82 and its 95% confidence interval (CI) 0.73-0.91. There was a decreased risk of cancers of the lung (SIR 0.35, 95% CI 0.25-0.48), especially among endurance athletes (0.12, 0.01-0.41). This fits well with the low prevalence of smoking among the athletes. The SIR for kidney cancer was also significantly low (0.43, 0.16-0.93), possibly partly due to the better diet (more vegetables, less fat). Incidence of cancers not related to smoking was not reduced. None of the cancer sites showed a significant excess in the whole cohort but hurdlers had a significantly high relative risk of sarcomas of the bone and soft tissue which according to suggested causal mechanisms might be related e.g. to injuries during their active sport period. This as well as other observations without sound a priori hypotheses needs to be confirmed in more detailed analyses and in other data sets before final conclusions.
Cigarette smoking and alcohol use habits in Finland and Sweden were studied using data from the Finnish and Swedish studies on like-sexed adult twin pairs aged 18-47 (total of 20 056 pairs). Finnish men were heavier consumers of tobacco and alcohol than Swedish men. When heavy consumers (greater than 500g of alcohol/month and greater than 20 cigarettes/day) were considered, the prevalence rate was 9.7% in Finnish men and 5.1% in Swedish men. This difference might account for the higher morbidity in Finland than in Sweden from many smoking- and alcohol-associated diseases. Genetic factors in smoking and alcohol use were assessed by comparing observed and expected coincidence rates, and by multivariate analyses. Genetic and familial effects were defined as an excess coincidence in monozygotic (MZ) pairs compared to dizygotic (DZ) pairs, and by an increased DZ coincidence rate compared to that expected. Significant genetic and familial effects were observed for cigarette smoking, and for smoking more than one pack of cigarettes a day. Significant familial effects for alcohol use was observed, and a significant genetic effect was obtained for men. A significant genetic effect could not be observed for the combined heavy use of alcohol and heavy smoking. The genetic and familial effects seemed to be mostly independent of country and sex.
Two large-scale studies of adult like-sexed twin pairs are ongoing in Sweden and Finland. Both studies comprise an unselected series that has been studied in a comparable fashion. Zygosity determination and health questionnaire data-gathering were carried out in 1973 for the Swedish study and in 1975 for the Finnish study for the comparable age groups. Data on hospital usage, cancer incidence and mortality are collected by record-linkage from the respective national registries. Cross-national twin studies can permit testing of hypotheses of the relationships between genetic and cultural factors and major chronic diseases and their risk factors.
Kinships composed of twin parents, their spouses and children, offer a robust and flexible sampling design for research in genetic epidemiology. Families-of-twins designs circumvent some of the sampling problems that arise when independent data sets are combined, and these designs provide unique evaluations of maternal influences, assortative mating and X-linkage. Unfortunately, empirical studies of families of twin parents have been limited by relatively small samples and by the self-selection biases intrinsic in ascertainment of families from volunteer twin registries. A large and representative cohort of monozygotic and dizygotic twin parents, drawn from a population-based twin registry, provides the optimal sampling frame for twin-family research. This paper reviews the sampling considerations underlying the initial family study based on the Finnish Twin Cohort and evaluates the representativeness of the sampled twins. Spouses and adult children (over 18 years) of 236 pairs of twins, about equally divided by gender and zygosity, were evaluated by a postal questionnaire. Individual response rates exceeded 86% and in 464 of the 472 nuclear families (98.3%), at last one member of the twin's family completed the questionnaire. The sampled twins, selected for fecundity to maximize statistical power of the obtained data, were broadly representative of non-selected twins drawn from the Cohort, with whom they were matched on age, gender, and zygosity. Such results suggest that the Finnish Cohort has excellent potential for extended twin-family research designs.
A deterministic questionnaire method for zygosity determination is developed for use in epidemiological studies of adult twins. It is based on the answers of both members of a twin pair to two questions on similarity and confusion in childhood. The algorithm of the method is used to determine the zygosity status of a twin pair at two different levels of certainty. The validity of the method is tested by making blood marker determinations of 11 polymorphic marker systems fro a random sample of 104 twin pairs. The agreement between questionnaire and blood marker diagnosis was 100%, but the stricter level of certainty left 8.7% in the nonclassified group. The genetical representativeness of the sample is tested by the allele distribution of the markers as compared to the Finnish population data as well as by the distribution of the number of intra-pair differences in blood markers.