Suchergebnisse

The Study of Dementia in Swedish Twins is a study of dementia in a defined population of twins. The goals included estimating heritability of Alzheimer's disease and identifying risk and protective factors in twin pairs discordant for the disease. The data, including not only diagnoses and age of onset but also extensive information about potential environmental risk factors, are now archived as Study ICPSR 25963 at National Archive for Computerized Data on Aging, Inter-university Consortium for Political and Social Research, at the University of Michigan, and available for researchers to use. Up to the time of archiving, 215 cases of dementia have been identified from a base sample of 2,394 individuals.

The Study of Dementia in Swedish Twins is a study of dementia in a defined population of twins. The goals included estimating heritability of Alzheimer's disease and identifying risk and protective factors in twin pairs discordant for the disease. The data, including not only diagnoses and age of onset but also extensive information about potential environmental risk factors, are now archived as Study ICPSR 25963 at National Archive for Computerized Data on Aging, Inter-university Consortium for Political and Social Research, at the University of Michigan, and available for researchers to use. Up to the time of archiving, 215 cases of dementia have been identified from a base sample of 2394 individuals.

SummaryThis study investigates the dimensions of occupation, and distances between occupational categories, by using intra-pair differences in adult occupational position for identical twins reared apart. Status and farm dimensions of occupation were identified. The results validate the use of occupational status as a dimension of occupational position. The causes of individual differences for the derived status dimension were also evaluated, based on groups of identical and fraternal twins reared apart or together. Genetic effects accounted for a substantial amount of the variance in occupational status for men, while shared and non-shared environmental effects were of about equal importance. For women, genetic effects were less important, and shared and non-shared environmental effects accounted for more of the variation. The results confirm that genetic effects are important sources of the familial resemblance often found for occupational status for men.

AbstractThe idea of far transfer effects in the cognitive sciences has received much attention in recent years. One domain where far transfer effects have frequently been reported is music education, with the prevailing idea that music practice entails an increase in cognitive ability (IQ). While cross‐sectional studies consistently find significant associations between music practice and IQ, randomized controlled trials, however, report mixed results. An alternative to the hypothesis of cognitive transfer effects is that some underlying factors, such as shared genes, influence practice behaviour and IQ causing associations on the phenotypic level. Here we explored the hypothesis of far transfer within the framework of music practice. A co‐twin control design combined with classical twin‐modelling based on a sample of more than 10,500 twins was used to explore causal associations between music practice and IQ as well as underlying genetic and environmental influences. As expected, phenotypic associations were moderate (r = 0.11 and r = 0.10 for males and females, respectively). However, the relationship disappeared when controlling for genetic and shared environmental influences using the co‐twin control method, indicating that a highly practiced twin did not have higher IQ than the untrained co‐twin. In line with that finding, the relationship between practice and IQ was mostly due to shared genetic influences. Findings strongly suggest that associations between music practice and IQ in the general population are non‐causal in nature. The implications of the present findings for research on plasticity, modularity, and transfer are discussed.

AbstractThe possibility of genotype–environment interaction for memory performance and change was examined in 150 monozygotic (MZ) twin pairs from the Swedish Adoption Twin Study of Aging (SATSA). We used an MZ twin pair difference approach to examine the possibility that genotype was associated with intrapair variability and thus suggestive of genotype–nonshared environment interactions. Multiple 'variability genes' were found for longitudinal change in a semantic memory task including candidates coding for apolipoprotein E (APOE) and estrogen receptor alpha (ESR1) as well as serotonin candidates (HTR2Aand5HTT). One candidate also related to variability in change in episodic memory (5HTT). Of the significant associations observed, generally results indicated that MZ pairs who carry putative risk alleles were less variable than noncarriers, suggesting that noncarriers may be more sensitive to environmental contexts. We sought to 'contextualize' the possible nonshared environmental influences for found gene–environment (G × E) effects by considering intrapair differences in measured social and stress factors, including social support, life events and depressive symptoms. Results suggested that nonshared environmental influences associated with depressive symptoms may moderate the G × E relationship observed forESR1andAPOEand longitudinal semantic memory change whereby noncarriers of putative risk alleles may be relatively more sensitive to depressionevoking environmental contexts than carriers of the risk allele. Thus, the contexts that facilitate or reduce depressive symptoms may affect semantic memory resiliency dependent on genotype. Further work ought to consider larger sample sizes as well as consider additional social and contextual factors.

AbstractTo explore age-related mechanisms in the expression of recurrent headache, we evaluated whether genetic and environmental influences are a function of the reporting age using questionnaire information that was gathered in 1973 for 15- to 47-year-old Swedish twins (n =12,606 twin pairs). Liability to mixed headache (mild migraine and tension-type headache) was explained by non-additive genetic influences (49%) in men aged from 15 to 30 years and additive genetic plus shared environmental influences (28%) in men aged from 31 to 47 years. In women, the explained proportion of variance, which was mainly due to additive genetic effects, ranged from 61% in adolescent twins to 12% in twins aged from 41 to 47 years, whereas individual specific environmental variance was significantly lower in twins aged from 15 to 20 years than in twins aged from 21 to 30 years. Liability to migrainous headache (more severe migraine) was explained by non-addi-tive genetic influences in men, 32% in young men and 45% in old men, while total phenotypic variance was significantly lower in young men than in old men. In women, the explained proportion of variance ranged from 91% in the youngest age group to 37% in the oldest age group, with major contributions from non-additive effects in young and old women (15–20 years and 41–47 years, respectively) and additive genetic effects in intermediate age groups (21–40 years). While total variance showed a positive age trend, genetic variance tended to be stable across age groups, whereas individual specific environmental variance was significantly lower in adolescent women as compared to older women.

AbstractStudies have shown that familial aggregation is of importance for abdominal symptoms including irritable bowel syndrome and there are a few reports of a moderate heritability for irritable bowel syndrome. Sex differences in prevalence and incidence of irritable bowel syndrome have been demonstrated however less is known about sex differences in heritability. The objective was to investigate whether there were sex differences in heritability of irritable bowel syndrome while accounting for different prevalences among women and men in different age groups. A sample of 45,750 Swedish twins, whereof 16,961 were complete twin pairs, participated in a telephone interview. The sample was divided into three age groups (40–54, 55–64 and 65 years and older) and the diagnosis of irritable bowel syndrome was operationally defined with a number of disorder specific symptoms. Standard biometrical model fitting analyses were conducted using raw ordinal data from same-sex and opposite-sex twins. The prevalence of irritable bowel syndrome was greater among women than men and more prevalent at younger ages (e.g., women 10.3%, men 6.3% at ages 40–54 years vs. women 6.1%, men 4% at ages over 65 years). The heritability of the disorder was approximately 25% in all age groups. We found no evidence for sex differences in heritability in any of the age groups, however, models allowing prevalences of irritable bowel syndrome to differ between sexes and age groups fitted best.

AbstractThe aim of this study was to determine the influence of genetic factors on the first episode of acute myocardial infarction. Probandwise concordances, tetrachoric correlations and quantitative genetic analyses of liability were applied to data drawn from the Swedish Twin Registry and the Swedish Acute Myocardial Infarction Register. All same-sexed twin pairs born between 1886 and 1958 who were alive in 1987 were included in the analyses. Our results show that concordance rates for acute myocardial infarction in monozygotic (MZ) twins were similar across sexes (among males .26 and females .27). For dizygotic (DZ) twins the concordances were .20 for males and .16 for females, yielding a greater MZ–DZ concordance differential for females than males. Tetrachoric correlations were greater for MZ than DZ twins for both sexes (.49 for male MZ and .34 for male DZ-twins and .56 and .35 for female MZ and DZ twins respectively). Quantitative genetic analyses of liability resulted in equal variance components for males and females (.36) but significantly different thresholds (prevalences). In conclusion, liability to first occurrence of acute myocardial infarction is moderately influenced by genetic variants in both sexes. The familial influence on phenotypic variance is exclusively explained by additive genetic factors.

AbstractThe Swedish Twin Registry functions as research infrastructure containing information on 216,258 twins born between 1886 and 2015, of whom 86,199 pairs have zygosity determined by DNA, an intrapair similarity algorithm, or being of opposite sex. In essence, practically all twins alive and currently 9 years or older have been invited for participation and donation of DNA on which genomewide single nucleotide polymorphisms array genotyping has been performed. Content, management and alternatives for future improvements are discussed.

AbstractOptimism has a positive influence on mental and somatic health throughout lifetime and into old age. This association is mainly due to shared genetic influences, with some indication of sex differences in the heritability of these and related traits (e.g., depression and subjective wellbeing). Here we extend our initial study of Australian twins by combining with data available from Swedish twins, in order to increase the power to explore potential sex differences in the genetic architecture of optimism, mental and self-rated health and their covariation. Optimism, mental, and self-rated health were measured in 3053 Australian (501 identical female (MZf), 153 identical male (MZm), 274 non-identical female (DZf), 77 non-identical male (DZm), and 242 non-identical opposite-sex twin pairs, and 561 single twins; mean age 60.97 ± 8.76), and 812 Swedish (71 MZf, 53 MZm, 93 DZf and 67 DZm twin pairs, and 244 single twins; mean age 60 ± 14.3) twin individuals using the Life Orientation Test (LOT), the General Health Questionnaire (GHQ) and a single-item self-rating of overall health, respectively. In females all three traits were moderately heritable (.27–.47), whereas in males heritability was substantially lower (.08–.19), but genetic modeling showed that sex differences were not significant. The absence of significant sex differences, despite the consistent trend across the two cohorts, is likely due to a lack of power, raising the importance for future studies, on the same or similar traits, to utilize large samples and to keep the possibility of sex differences in mind when conducting their analyses.