We investigated whether BMI predicts type 2 diabetes in twins and to what extent that is explained by common genetic factors.
This was a population-based twin cohort study. Monozygotic (n = 4,076) and dizygotic (n = 9,109) non-diabetic twin pairs born before 1958 answered a questionnaire in 1975, from which BMI was obtained. Information on incident cases of diabetes was obtained by linkage to nationwide registers until 2005.
Altogether, 1,332 twins (6.3% of men, 5.1% of women) developed type 2 diabetes. The HR for type 2 diabetes increased monotonically with a mean of 1.22 (95% CI 1.20-1.24) per BMI unit and of 1.97 (95% CI 1.87-2.08) per SD of BMI. The HRs for lean, overweight, obese and morbidly obese participants were 0.59, 2.96, 6.80 and 13.64 as compared with normal weight participants. Model heritability estimates for bivariate variance due to an additive genetic component and non-shared environmental component were 75% (men) and 71% (women) for BMI, and 73% and 64%, respectively for type 2 diabetes. The correlations between genetic variance components (r (g)) indicated that one fifth of the covariance of BMI and type 2 diabetes was due to shared genetic influences. Although the mean monozygotic concordance for type 2 diabetes was approximately twice the dizygotic one, age of onset of diabetes within twin pair members varied greatly, irrespective of zygosity.
A 28-year follow-up of adult Finnish twins showed that despite high trait heritability estimates, only a fraction of covariation in BMI and incident type 2 diabetes was of genetic origin.
We have reported cross-sectional evidence that behavioral similarities of adult monozygotic (MZ) cotwins are associated with their age at initial separation and the frequency of their subsequent social interaction (Kaprio et al., 1987; Rose et al., 1988; Rose and Kaprio, 1988). Twins who separated early and twins in infrequent interaction were less alike. Data for those reports came from a 1981 survey of the Finnish Twin Cohort. The Finnish cohort had been surveyed in 1975 with a similar questionnaire, and we now report a longitudinal analysis of the 1975-1981 surveys. All cohabiting MZ cotwins, ages 18-25 at the 1975 baseline, were followed up in 1981, and pairwise similarities at baseline and follow-up were compared for three groups: MZ pairs that remained cohabiting, separated pairs in which the cotwins retained regular contact with one another, and separated cotwins whose social interactions at follow-up were infrequent. For alcohol consumption and EPI Neuroticism scores, relative similarities of the MZ cotwins at follow-up paralleled the relative frequencies of their social contact; baseline differences in resemblance for Extraversion scores preceded follow-up differences in social interaction. These findings clarify the directional nature of associations found in our cross-sectional data and provide new, more compelling evidence of effects of shared experience on sibling resemblance for some dimensions of adult behavior.
The relative roles of genetic and environmental factors in sciatica were studied in the nationwide Finnish twin panel consisting of 9365 adult pairs of the same gender. Morbidity was analysed from two sources of data: the life-long cumulative incidence was measured by a postal questionnaire, and the rate of hospital admission during a 14-year period was measured by record-linkage of the twin panel and the nationwide hospital registry. Altogether 2220 individuals reported sciatica diagnosed by a doctor and 304 were admitted to hospital with a diagnosis of sciatica. The proportion of concordant pairs (calculated from affected pairs) was 17.7% for monozygotic and 12.0% for dizygotic pairs in the life-long cumulative incidence of reported sciatica, and correspondingly 4.6% and 1.9% for those admitted to hospital (a 14-year period) because of sciatica. The estimated heritability was 20.8% for those with reported sciatica and 10.6% for those admitted to hospital. The results show that environmental factors account for more than 80% of the etiology of sciatica, and more than 90% in the case of patients admitted to the hospital. Genetic factors, however, were relatively more significant in individuals under 40.
Cancer incidence in 433 McKee-Farrar total hip replacement patients, operated on between 1967 and 1973, was examined for 5729 person-years, to the end of 1981. The expected number of natural deaths was slightly higher than observed, suggesting some selection of the operated patients. The risk of total cancer incidence did not increase, but the risk for site-specific cancer did because there were no cases of kidney or bladder cancer, or rare forms of cancer. The risk of leukemias and lymphomas increased, and the risk of breast cancer decreased; these results were surprisingly similar to those of a study from New Zealand. This study concluded that patients with total hip prostheses have a cancer morbidity differing from the general population. The role of chrome-cobalt-molybdenum alloy in carcinogenesis requires further investigation.
Associations of psychosocial factors with interpersonal conflicts at work were studied in a sample drawn from the Finnish population using a mailed questionnaire. The sample consisted of 14,578 employees aged 24-64 years. The frequency of interpersonal conflicts at work was equal among both sexes. Our results suggest that occupational factors such as hectically paced work, monotonous work and white collar status are associated with interpersonal conflicts at work; and more conflicts are found in the younger age-groups. In the multivariate analyses, dissatisfaction with life, daily stress, neuroticism and hostility were found to be the significant risk factors for interpersonal conflicts at work for both sexes, whereas a higher educational level was a considerable risk factor only for men, and low self-assurance only for women. Among men the combination of hectically paced and monotonous work was also found to be a significant risk factor. The results indicate complexity of the concept of human relationships at work, and the importance of both occupational factors and psychological characteristics.
A population-based epidemiological study of the prevalence of headache in a sample of 24,682 adults was carried out in Finland. Enquiries were made concerning the frequency of headache, migraine and characteristics of headache attacks in a questionnaire survey in 1981. Headache was classified as migraine, and headache without migrainous features. Possible somatic causes of headache were excluded by record-linkage with three nation-wide medical registries. The prevalence of both headache types depended on age and gender. Among women the overall prevalence of migraine was 10.1% with a maximum of 11.5% in the 40-49 age group. The prevalence rate among men was 2.5% and the female/male gender ratio was 4.0. Women with migraine had an average of 52.5 headache occasions during a year and men with migraine 61 headache occasions per year. At the individual level, headache without migrainous features was least invalidating. There were only 16.5 headache occasions a year among women and 11.5 among men. However, from a population perspective headache without migrainous features accounted for 46.5% of all headache occasions among women and for 60.8% among men. Thus, from the public health view-point, studies of "non-clinical" headache, e.g. headache without migrainous features should be emphasized.
Findings of an early arthroscopy performed in 108 consecutive hemarthrotic and clinically stable knees were analyzed. The patients were young conscripts, the mean age being 19.9 years. Fifty-seven of the knees were injured during military training, 36 in different sports activities, 9 at falls, and 6 in motorbike accidents. The lesions were divided into "primary" (lesions needing operative treatment or the supposed most common lesions in incidence) and "secondary" (other lesions). An average of 1.6 lesions were observed per knee. Dislocation of the patella was the most common diagnosis in 38 (35%) cases. Dislocation of the patella was associated with military exercise (p
The Finnish Twin Cohort study (27,776 individuals; all twins of the same sex born before 1958 and alive in 1967) detected 316 cases of epileptic seizures occurring in 310 twin pairs: 89 monozygotic pairs and 221 dizygotic pairs, including three concordant monozygotic pairs and three concordant dizygotic pairs. The ratio of the observed to expected number of concordant pairs for epileptic seizures was 5.48 (90% CL 1.5-14.2) in monozygotic and 2.12 (90% CL 0.6-5.5) in dizygotic pairs. The results suggest that 8% to 27% of the incidence of epileptic seizures is related to genetic variability. The study of environmental differences in discordant monozygotic pairs should provide insights into the etiology of this group of disorders.
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.
We studied the cumulative incidence, concordance rate and heritability for diabetes mellitus in a nationwide cohort of 13,888 Finnish twin pairs of the same sex. The twins were born before 1958 and both co-twins were alive in 1967. Data on diabetes were derived through computerized record linkage from death certificates, the National Hospital Discharge Register and the National Drug Register. Records were reviewed in order to assign a diagnostic category to the 738 diabetic patients identified. Of these patients 109 had Type 1 (insulin-dependent) diabetes, 505 Type 2 (non-insulin-dependent) diabetes, 46 gestational diabetes, 24 secondary diabetes, 38 impaired glucose tolerance and 16 remained unclassified. The cumulative incidence of diabetes was 1.4% in men and 1.3% in women aged 28-59 years and 9.3% and 7.0% in men and women aged 60 years and over, respectively. The cumulative incidence did not differ between monozygotic and dizygotic twins. The concordance rate for Type 1 diabetes was higher among monozygotic (23% probandwise and 13% pairwise) than dizygotic twins (5% probandwise and 3% pairwise). The probandwise and pairwise concordance rates for Type 2 diabetes were 34% and 20% among monozygotic twins and 16% and 9% in dizygotic twins, respectively. Heritability for Type 1 diabetes was greater than that for Type 2 where both genetic and environmental effects seemed to play a significant role.