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ABSTRACT: Similarities for Extraversion (E) and Neuroticism (N) scale scores from the Eysenck Personality Inventory were evaluated in 7,144 adult twin pairs, drawn from the population-based Finnish Twin Cohort, as a function of the co-twins' genetic resemblance, gender, age, and the frequency of their social interaction with each other. To separate effects of shared genes from those of shared experience, we performed hierarchical multiple regressions of double-entry data matrices. Results establish the predictive significance of both genetic and experiential influences: Genetic effects remained significant when tested after the effects of social contact were first removed; conversely, for N scores, the effects of social contact remained significant when assessed after genetic influences were first removed. These findings establish genetic variance in major dimensions of adult personality but assign a significant role to common experience as well. The first finding constructively replicates reports by others; the second challenges the widespread assumption that shared experiences have a negligible impact on sibling similarity in adult personality.
Journal of Personality and Social Psychology 02/1988; 54(1):161-71. · 5.08 Impact Factor
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ABSTRACT: To evaluate genetic influences on the use and abuse of alcohol, we compared questionnaire measures of the frequency, quantity, and density of social drinking, and the frequency of alcohol-induced passouts self-reported by 879 monozygotic (MZ) and 1940 dizygotic (DZ) pairs of twin brothers, aged 24-49 yr. The measures of frequency, quantity, and density (heavy drinking once or more a month) significantly intercorrelate, and the self-reported alcohol consumption by this sample is satisfactorily stable and consistent with nationwide sales figures. None of the drinking measures was associated with twin type (zygosity), and only density correlated with age. Similarity of drinking habits among twin brothers was evaluated as a function of their genetic resemblance and age, the frequency of their social contact with one another, and the interactions of these terms. The effects were estimated from hierarchical linear regressions of a double-entry data matrix from which each twin's drinking was predicted from that of his twin brother, and that pair's age, zygosity, cohabitation status, and frequency of social contact. Significant genetic variance was found for each of the drinking measures with heritability estimates ranging from 0.36 to 0.40. Co-twins in more frequent social contact with one another reported greater similarity in their use of alcohol, but heritable variance remained after the effects of age and social contact were removed from both mean levels and co-twin resemblance. Reported frequency of passouts yielded significant, but equivalent, correlations in both MZ and DZ twins and no evidence of genetic influence.
Alcoholism Clinical and Experimental Research 09/1987; 11(4):349-56. · 3.34 Impact Factor
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ABSTRACT: 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.
Acta geneticae medicae et gemellologiae 02/1987; 36(1):79-93.
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ABSTRACT: The self-reported alcohol use of 12994 Finnish adults were followed up six years and the changes of alcohol consumption among males and females were analysed.
Alcohol and alcoholism (Oxford, Oxfordshire). Supplement 02/1987; 1:619-23.
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ABSTRACT: Hierarchical multiple regression analyses of questionnaire data reported by male twins in the Finnish Twin Cohort were used to evaluate genetic and social influences on use and abuse of alcohol. The similarity in drinking patterns of twin brothers is related to the frequency of their social interaction, and monozygotic co-twins are in more frequent social contact. But the stepwise multiple regressions show that the greater social interaction of identical twins cannot account for their greater similarity in drinking patterns. We conclude that genetic variance significantly contributes to population variance in the frequency, quantity, and density of social drinking.
Alcohol and alcoholism (Oxford, Oxfordshire). Supplement 02/1987; 1:373-7.
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ABSTRACT: The components of the decline in mortality from ischaemic heart disease in Finland were studied by analysing the changes in incidence and prognosis between 1972 and 1981. Using personal identification numbers, hospital discharge records and death certificates were linked for all men and women aged 40-64. During this period mortality decreased 15.9% in men and 23.5% in women, incidence 14.2% in men and 19.3% in women, being greatest among 40-49 year olds living in urban areas, and case fatality 7.3% in men and 10.3% in women, owing primarily to a decrease in patients dying of ischaemic heart disease without being admitted to hospital; survival was also better among patients admitted to hospital. Factors explaining these changes remain unknown because data on risk factors and factors influencing prognosis are limited and largely ecological.
British medical journal (Clinical research ed.) 07/1985; 290(6484):1773-5.
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ABSTRACT: The association of snoring with hypertension and ischaemic heart disease (IHD) was tested by postal questionnaire in a population of 3847 men and 3664 women aged 40-69 years. Hypertension associated highly significantly with snoring, the relative risk (RR) of hypertension between habitual snorers and never snorers being 1.94 in men and 3.19 in women. This association was also found when adjusting for body-mass index. A significant association between angina pectoris and habitual snoring was observed in men (RR = 2.22). In women the relative risk was not significant. An association between habitual snoring and angina pectoris in men was also found after adjusting for hypertension and body-mass index (RR = 2.01, p less than 0.01). The relative risks for myocardial infarction and hospital admission for IHD for habitual snorers were non-significant.
The Lancet 05/1985; 1(8434):893-6. · 38.28 Impact Factor
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ABSTRACT: Data on alcohol use and smoking habits was available from the 1975 questionnaire of the entire cohort. Prior to pairwise analyses, the data of individuals was compared to that of age-sex matched groups of pairs reared together. The early separated twins had a higher alcohol consumption, while for smoking only slight differences were observed compared to twins reared together. Probandwise concordance rates were computed from smoking status (ever smoker/never smoker), alcohol use (user/nonuser) and "heavy" drinking (half-bottle of spirits on one occasion at least once a month). The following results were obtained in those pairs with the environmental dissimilarity score greater than 15: (table; see text)
Acta geneticae medicae et gemellologiae 02/1984; 33(3):425-33.
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ABSTRACT: Hospitalization rates of monozygotic (MZ) and dizygotic (DZ) twin pairs in Finland were compared for schizophrenia, neuroses, and alcoholism. Record-linkage of hospital records and death certificates for the years 1972-1979 was carried out for persons in the Finnish Twin Cohort (16,649 like-sexed twin pairs). The ratio of the number of observed vs that of expected concordant pairs and the ratio of concordance rates between MZ and DZ pairs were greater among males than females, and greater among young (40 years old or less) than among older pairs. The highest difference was found in schizophrenia and the lowest in neuroses. Pairwise concordance rates for schizophrenia (11.0% for MZ and 1.8% for DZ) seem to indicate great environmental influence (high proportion of discordant pairs) with apparent genetic liability (6.1-fold ratio in concordance between MZ and DZ pairs). In neurotic disorders, the difference of pairwise concordance rates between MZ and DZ pairs (6.8% vs 4.0%) was quite low, not strongly supporting a genetic hypothesis. Of the MZ pairs concordant for psychiatric hospitalization, 47% had lived together for their whole life time; of those discordant, 16% lived together. The corresponding figures for DZ pairs were 18% and 15%. The effect of intrapair relationships in disease-concordant pairs should be taken into account when evaluating the effect of genetic and environmental factors in psychiatric disorders.
Acta geneticae medicae et gemellologiae 02/1984; 33(2):321-32.
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ABSTRACT: This study is based on data from 165 adult twin pairs separated at 10 years or less. Information on personality factors: extraversion (E) and neuroticism (N) (EPI scale short from), life satisfaction (LS) (Allardt) and stress of daily activities (SDA) was obtained as part of the questionnaire study carried out in the entire Finnish Twin Cohort in 1975. Later in 1979 a questionnaire sent to the twins reared apart yielded a scale (range 7-30 points) measuring the environmental dissimilarities after separation (reliability 0.83). The effect of separation on personality factors by analysis of variance of individual data was studied. Sex, zygosity and age-at-separation were included in the models. The overall explanatory rates were low (2.1-4.4%). The definitive study group was formed by selecting those pairs with a dissimilarity score greater than 15. The following intraclass correlations were obtained.
Acta geneticae medicae et gemellologiae 02/1984; 33(2):259-64.
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ABSTRACT: Within the Finnish Twin Cohort of like-sexed adult twin pairs, a subgroup of pairs separated at an early age has been identified. In 165 pairs, both cotwins responded to questionnaires in 1975 and 1979. An environmental dissimilarity score was formed which consists of items on whether the twins had lived after separation in the same community, attended the same school, were on the same grade at school, how often the cotwins met, how often they met common friends and relatives and whether they attended the same clubs etc, or not. To validate the zygosity diagnosis obtained by questionnaire in 1975, those pairs whose zygosity was unknown as well as those with the least contact after separation were contacted for blood sampling (11 bloodgroups). Of 15 pairs with no zygosity diagnosis, 10 responded (1 no address,2 abroad,2 refused). Six pairs were classified MZ and 4 DZ. In 12 MZ and 8 DZ pairs undergoing bloodgroup determination, the classification of only one pair changed from DZ to MZ. The following intraclass correlations for height and weight were found.
Acta geneticae medicae et gemellologiae 02/1984; 33(2):251-8.
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ABSTRACT: Some health related psychosocial correlates of the Eysenck neuroticism scale were examined in a questionnaire study of 1501 monozygotic (MZ) and 3455 dizygotic (DZ) male twin pairs representing the adult male twin population in Finland. In analyses of the individuals, 34% of the variance in neuroticism was associated to: psychological variables (stress of daily activities, life satisfaction, quality of sleep, and extroversion - the explanatory rate of this variable set was 30%), psychotropic drugs (5%), alcohol use (4%), and smoking (2%). Neuroticism was also associated to social, life change, and medical variables. In pairwise analyses, the heritability estimate (h2) was 0.54 for pairs living together and 0.39 for pairs living apart. It seems that heritability estimates are confounded by the closer intrapair relationship between members of MZ than DZ pairs. In pairwise analyses, 23% of the intrapair difference of neuroticism in MZ pairs was associated to intrapair differences in the aforementioned variables. The following explanatory rates were found: psychological variables, 21%; psychotropic drugs, 2%; alcohol use, 2%; and smoking, 1%. Neuroticism of pairs discordant for background variables showed similar intrapair differences as between individuals in the following variables: service vs farming work, use of alcohol, use of antacids, hypertension, heavy physical work, quality of sleep, changes of workplace for negative reasons, smoking, and use of tranquillizers. It appears that in Finland environmental factors explain at least 61% of the variability in neuroticism, and that factors determining neuroticism are also associated to health related behavior such as smoking, use of alcohol and psychotropic drugs.
Acta geneticae medicae et gemellologiae 02/1984; 33(2):307-20.
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ABSTRACT: Self-reported sleep data from 2238 monozygotic and 4545 dizygotic adult twin pairs indicated a significant hereditary effect on sleep length [overall heritability estimate (h2 = 0.44)] and on sleep quality (h2 = 0.44). When the data were examined in subgroups defined by sex, age (18-24 years and 25 or more years of age), and cohabitation status of the twin pair, the highest heritability estimates for sleep length were for twins living together aged 25 or older. For twins living apart the heritability estimates were statistically significant in all women and men aged 25 or older. For sleep quality significant heritability estimates were found for all groups except women living together.
Sleep 02/1983; 6(3):179-85. · 5.05 Impact Factor
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ABSTRACT: Ischemic heart disease is more common in East Finland than in West Finland, but systematic comparison and follow-up of incidence figures have not been possible. In 1972 the personal identification number became included in the hospital discharge records, which made it possible to link death certificate data with hospital records from the whole country. The results of this study suggest that high mortality from IHD in some regions is more closely associated with high incidence than a high fatality rate. The proportion of deaths outside hospitals showed large variation by province but this had rather little effect on the total one-year survival rates.
Acta medica Scandinavica 02/1982; 212(6):355-60.
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ABSTRACT: Increased mortality from ischaemic heart disease (IHD) has been found in previous studies among divorced, widowed, and unskilled middle-aged Finnish men. In this study all cases of IHD in men aged 40-64 during 1972 were analysed by linking death certificates and hospital records (7499 cases with 3136 deaths). Age-adjusted incidence, mortality, and survival rates of the first and third year were calculated by marital status and social class. The highest mortality rate was found among unskilled workers, the highest incidence among widowers and those in the lower professional classes, and the lowest survival rate among divorcees, single persons, and unskilled workers. The ratio of mortality by marital status (1.77) was in part due to survival (ratio 1.44) and in part due to incidence (ratio 1.32). The ratio of mortality by social class (1.44) seemed to be due more to differences in incidence (ratio 1.36) than to differences in survival (ratio 1.18). The distribution of conventional risk factors of IHD by marital status and social class seems to explain only part of the mortality differences.
Journal of Epidemiology & Community Health 10/1981; 35(3):192-6. · 3.19 Impact Factor
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Journal of Chronic Diseases 02/1981; 34(7):331-40.
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Progress in clinical and biological research 02/1981; 69 Pt C:23-35.
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Progress in clinical and biological research 02/1981; 69 Pt C:139-48.
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Progress in clinical and biological research 02/1981; 69 Pt B:189-98.
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ABSTRACT: We report the association between hostility and the incidence of ischemic heart disease (IHD) in 3,750 Finnish men aged 40-59. Hostility was assessed from self-ratings on irritability, ease of anger-arousal, and argumentativeness, and four groups were formed from the summed hostility ratings. At baseline, the age-adjusted relative risk (RR) of the prevalence of angina pectoris between the highest and lowest hostility groups was 2.88 (95% confidence limits (CL), range 1.71-4.77). A three-year follow-up yielded 65 deaths and 109 IHD-incident cases. Hostility did not predict IHD among healthy men, but among men with previous IHD and hypertension (N = 104), the age-adjusted RR of IHD between the highest and lowest hostility groups was 12.9 (95% CL, 3.92-42.6). After standardization for smoking, obesity, heavy alcohol use, and snoring, the RR was 14.6 (95% CL, 1.94-110). When the degree of dyspnea at baseline was also standardized, the RR was 21.1 (95% CL, 1.59-282). Our data suggest that extreme hostility is not a consequence of symptom severity; rather, hostility is a strong determinant of coronary attack among hypertensive men with IHD.
Psychosomatic Medicine 50(4):330-40. · 3.97 Impact Factor
