Biomedical subjects

K Tambs

Publications and source records attributed to K Tambs.

At least 37 records · Page 2Linked to original sources

PubMed1998

Is there a consequence for fetal growth of having an unlike-sexed cohabitant in utero?

BACKGROUND: There is evidence to suggest a masculinizing effect on female intrauterine development in unlike-sexed twins. The purpose of the present report was to examine the possible effects of male presence on fetal growth in females by comparing mean birthweights in members from dizygotic unlike-sexed (DZU) pairs with those from dizygotic like-sexed (DZL) pairs. METHODS: The sample consisted of 1087 DZU and 1089 DZL twin pairs from the New Norwegian Twin Panel, which was established by identifying all twin births from 1967 to 1974 through the population-based Medical Birth Registry. RESULTS: The mean birthweight of females from DZU pairs was 2684+/-15 g (+/-SEM), as opposed to 2647+/-19 g in females from DZL pairs (P = 0.06). For males, the mean birthweight was 2812+/-16 g in DZU pairs and 2805+/-20 g in DZL pairs (P= 0.78). CONCLUSION: We found a tendency for the birthweight in females to be influenced by the presence of a male co-twin. This observation may have a biological significance and should lead to a close follow-up of DZU and DZL females with respect to hormone-sensitive disorders and reproductive ability.

Birth Weight↗

PubMed1997

Genetic and environmental contributions to the correlation between alcohol consumption and symptoms of anxiety and depression. Results from a bivariate analysis of Norwegian twin data.

Two thousand five hundred seventy pairs of Norwegian MZ and like-sexed and unlike-sexed DZ twins aged 18-25 years completed questionnaires with information about symptoms of anxiety and depression and alcohol consumption. The aim of the study was to estimate sex-specific genetic and environmental effects unique to symptoms of anxiety/depression and to alcohol consumption and effects common to the two phenotypes. Five models fitted the data almost equally well. The heritability estimate from these models ranged from .23 to .57 for male alcohol consumption, from .39 to .59 for female alcohol consumption, from .25 to .48 for male anxiety/depression, and from .45 to .56 for female anxiety/depression. The phenotypic correlation between alcohol and anxiety/depression in males (r = .23) could be fully explained by common genetic effects. The correlation in females (r = .18) was caused by individual environmental factors together with either genetic effects or family environment.

Adolescent↗

PubMed1997

No evidence for effects of family environment on asthma. A retrospective study of Norwegian twins.

The risk of developing asthma contingent upon the co-twins' history of asthma was analyzed in a population-based study of 5,864 Norwegian twins. A primary aim was to assess the significance of shared environment for the development of asthma from infancy through age 25. Retrospective reports were collected when the twins were 18 to 25 yr of age. The risk of developing asthma, contingent upon the co-twin's history of asthma, was estimated using survival analyses, and genetic and environmental sources of variation in liability for asthma were analyzed with structural equation models. The cumulative incidence of asthma was 6% for males and 5.4% for females. The relative risk of developing asthma among twins whose co-twin had a positive history of asthma compared with those whose co-twin had no history of asthma was 17.9 (95% CI, 10.3 to 31.0) for identical, and 2.3 (95% CI, 1.2 to 4.4) for fraternal twins. Although shared environment encompasses many of the exposures that are putative risk factors for asthma in this age range, there is no evidence of shared environmental influences for asthma. Rather, 75% of the variation in liability for asthma was explained by genetic effects and the remaining variation was due to nonshared environmental influences. These results suggest that the familial risk for asthma is primarily, genetic.

Actuarial Analysis↗

PubMed1997

Distribution and heritability of recurrent ear infections.

The distribution of recurrent ear infections was obtained from a population-based sample of 2,750 pairs of Norwegian twins born between 1967 and 1974. The lifetime prevalence of self-reported recurrent ear infections was 8.9%, with a significant predominance of female cases. The mean age of onset was 4.2 years, with a gradual decrease in occurrence from 2 to 7 years of age. Among monozygotic pairs, the rate of tetrachoric correlation between co-twins was almost identical in males (0.73, SE 0.08) and females (0.74, SE 0.06), but among the dizygotic pairs the correlation was clearly higher in males (0.53, SE 0.12) than in females (0.20, SE 0.12). The value in the unlike-sexed dizygotic twins (0.25, SE 0.05) was intermediate to that of the like-sexed male and female dizygotic pairs. The relative contribution of genes and environment to variability in the predisposition to develop otitis media was estimated by means of structural equation modeling. Variation in liability to ear infections was mainly explained by additive genetic and dominance factors in females, for whom heritability was estimated at 74%. The remaining 26% of the variation in liability was explained by individual environmental factors. In males, 45% of the variation could be accounted for by genetic factors, 29% by common familial environment, and the remaining 26% by individual environmental effects.

Acute Disease↗

PubMed1997

Urban environment and mental health. A longitudinal study.

BACKGROUND: In a follow-up survey from Oslo, 503 persons were re-interviewed using the same questionnaire after 10 years. METHOD: The questionnaire includes questions about social support, social characteristics of the neighbourhood and mental health. Information about the neighbourhood was also gathered from key informants. RESULTS: Of the five types of neighbourhoods surveyed, only one showed marked change over time with respect to social characteristics. This was an initially poorly functioning neighbourhood with poor mental health among the residents, where substantial improvements took place as part of the further development of the area. Parallel with the improvement in social environment there was a significant improvement in mental health among those who continued to live in the same area, as opposed to those who continued to live in the other areas. Selective migration could not explain this finding. CONCLUSIONS: The findings support the environment stress hypothesis, implying that the quality of a neighbourhood has an impact on mental health. The implications for psychiatric prevention are discussed.

Age Factors↗

PubMed1996

Otitis media: relationship to tonsillitis, sinusitis and atopic diseases.

In order to estimate the co-morbidity between ear infections and related childhood diseases, data about the occurrence of recurrent ear infections, tonsillitis, sinusitis and atopic diseases from a population based sample of 7992 Norwegian twins were analysed. Correlational results revealed two general clusters, one consisting of upper respiratory tract infections (URI), the other defined by the atopic diseases. Overall, associations between the diseases were greater in males. The sizes of the correlations within each subgroup of infections were moderate, but significant, ranging from 0.191 to 0.363. Similar results were found for the relationship within the subgroup of atopies, with correlations ranging from 0.134 to 0.466. The correlations between the infectious and atopic diseases were weak. Both ear infections and tonsillitis seemed to be predisposing factors for sinusitis. The relative risk of sinusitis among individuals with a history of ear infections was 3.4 (1.9-6.2) and 1.9 (1.2-3.0) for males and females, respectively. Ear infections conferred an increase in tonsillitis, estimated at 2.3 (1.6-3.0) and 2.0 (1.2-3.6) for males and females, respectively. In conclusion, the present study finds evidence for a common predisposition of upper respiratory infections as well as for atopic diseases, but only moderate correlation between the subgroups. Specifically, between ear infections and hay fever there was no covariation.

Adolescent↗

PubMed1996

The relationship between otitis media and intrauterine growth: a co-twin control study.

The association between intrauterine growth, as measured by weight and gestational age, and the occurrence of recurrent ear infections was studied using data from a population-based sample of 7992 Norwegian twins. Perinatal measures were collected from the Medical Birth Registry, and reports of recurrent ear infections were based on questionnaires completed when the twins were aged 18-25 years. First, the individual effects of birth weight and gestational age on the occurrence of otitis media (OM) were estimated Birth weight among individuals who reported OM was significantly lower than for controls, with a mean weight difference of 86 g. The average difference in gestational age was 3 days shorter among individuals with a positive history of OM. Next, the effect of birth weight was estimated using the co-twin control method. Among MZ twins, within-pair differences in birth weight reflect environmental differences experienced in utero. Among DZ pairs, birth weight differences may be due to genetic and environmental differences. Among OM-discordant pairs, the co-twin without a history of OM is a matched control for comparisons of intra-pair differences in birth weight. When within-pair birth weight differences were compared, the co-twin without a history of OM was used as the matched control. Results indicated that lower birth weight may be a risk factor for OM. The average birth weight difference among OM-discordant pairs was 48 g, with the control twin weighing significantly more than the twin with a history of OM.

Adolescent↗

PubMed1995

Sex-specific effects for body mass index in the new Norwegian twin panel.

Sex-specific effects for body mass index (BMI) were explored in a newly established, population-based Norwegian twin panel. The sample includes 5,864 individuals, aged 18-25 years, who responded to a questionnaire containing items for zygosity classification, height, weight, health, health-related behaviors, well-being, and demographic information. Among the 2,570 intact pairs who returned the questionnaire there were 416 identical (MZ) male pairs, 387 fraternal (DZ) male pairs, 528 MZ female pairs, 443 DZ female pairs, and 796 unlike-sexed pairs. Alternate sets of models testing for either sex-specific genetic or environmental parameters were evaluated using structural equation analysis. Results from the most parsimonious model indicated that the genes contributing to variation in BMI are not identical for men and women; rather, some genetic effects were shared by the sexes and some were unique to each sex. Total variation in BMI could be explained by sex-specific additive genetic effects, as well as genetic and non-shared environmental effects common to men and women. Estimates of heritability were .708 for men and .789 for women, and the male-female genetic correlation was 0.622. The series of models specifying sex-specific shared environment also fit the data and suggests that shared environmental factors may be important for males but not for females. The findings raise questions concerning the relationship between sex-specific effects for BMI and sex differences in health outcomes.

Adolescent↗

PubMed1995

Sex-specific causal factors and effects of common environment for symptoms of anxiety and depression in twins.

Two thousand five hundred seventy intact pairs and 724 single responders from Norwegian twins aged 18-25 years completed questionnaires with information about anxiety and depression and perceived cotwin closeness. The aim of the study was the univariate estimation of sex-specific genetic and environmental effects on an index tapping symptoms of anxiety and depression. An index of social closeness between cotwins was significantly related to the cotwin correlation for anxiety/depression scores. MZ pairs were reported to be closer than DZ pairs, and like-sexed DZ pairs were closer than unlike-sexed pairs. The symptom data were adjusted for this apparent violation of the "equal-environment" assumption in twin studies, but the adjustment did not dramatically affect the parameter estimates of genetic and environmental effects on anxiety/depression. A model specifying male (aM) and female (aF) genetic additive effects, shared environment for males (cM), and individual environmental effects (eM and eF) fitted the adjusted data very well. An alternative model, specifying aM = aF, cM = cF, and eM = eF, and no correlation between those environmental factors shared by brothers and those shared by sisters, fitted equally well. Estimated proportions of total variance from the first model were aM2 = .30, aF2 = .52, and cM2 = .21. The estimates from the second model were aM2 = aF2 = .43 and cM2 = cF2 = .11.

Adolescent↗

PubMed1995

Diabetes mellitus and psychological well-being. Results of the Nord-Trøndelag health survey.

The present study relies on questionnaire data from a diabetes and hypertension screening carried out on the entire adult population of a medium-sized Norwegian county (total number of participants = 74,977). Self-reported diabetic patients were compared with non-diabetics, and with patients with self-reported angina pectoris, previous cardiac infarction, and stroke. The psychological well-being of the known diabetic patients was found to be significantly poorer than that of those without diabetes, but better than that of those with angina and stroke. HbAl level was found to be significantly related to well-being, the low levels of HbAl (below 7.5%) scoring low on well-being and the high levels (above 15%) scoring high. Because of its special design, the present study allowed comparisons between diabetic patients undergoing treatment and newly detected patients who had not yet been treated. Treatment-related interpretations therefore could be rejected.

Adult↗

PubMed1995

Social support, negative life events and mental health.

BACKGROUND: In a 10-year follow-up of a survey from Oslo, 503 persons were reinterviewed using the same questionnaire. METHOD: The questionnaire includes information about social support, 'locus of control' and mental health as well as negative life events and long-lasting mental strain during the year prior to the follow-up. RESULTS: The study confirms the "buffer hypothesis", that social support protects against the development of mental disorder only when the individual is exposed to stressors, like negative life events. This buffering effect was especially strong for depression. CONCLUSIONS: The buffering effect only applies to the 'externals'--those who have personality-related feelings of powerlessness and lack of control over their own lives. The 'internals' do not have the same need for social support to cope with life stressors, and have low symptom scores even when negative life events are combined with relative weak social support.

Adaptation, Psychological↗

PubMed1994

No differential heritability of intelligence test scores across ability levels in Norway.

The possibility of differential heritability of intelligence test scores across levels of ability has been raised in several recent reports. In the present paper intelligence test data from 862 monozygotic and 1325 dizygotic male twin pairs tested at about 19 years of age were analyzed in search for changes in heritability and shared environmentality as a function of ability level. The analyses were performed by means of multiple regression models (e.g., Cherny et al., 1992). No evidence of differential heritability across different ability levels was detected.

Adult↗

PubMed1993

Low genetic effect and age-specific family effect for symptoms of anxiety and depression in nuclear families, halfsibs and twins.

Questionnaire information on symptoms of anxiety/depression was obtained from 61,286 persons, most of whom could be grouped in families as spouses, parents, offspring, siblings, halfsibs and twins. The correlations between mental health in relatives, varying somewhat by sex, were: 0.27 for 18,768 pairs of spouses, 0.12 to 0.17 for 30,888 pairs of parents and offspring, 0.11 to 0.18 for 13,134 pairs of siblings, 0.27 to 0.35 for 57 pairs of MS twins, -0.06 to 0.10 for 60 pairs of DZ twins, 0.30 for 88 pairs of halfsibs reared together, and 0.16 for 40 pairs of halfsibs reared apart. The heritability was estimated to be between 0 and 0.20. There was a significant effect of environmental transmission from mother, but not from father, to offspring. The effect of environmental factors shared by sisters was substantial, the corresponding effect was lower in brothers, and zero in siblings of opposite sex. The correlations decreased with increasing age differences between relatives, implying effects of age-specific genes or environmental factors in the family.

Adolescent↗

PubMed1993

How well can a few questionnaire items indicate anxiety and depression?

There is a need for a short form questionnaire with known psychometric characteristics that may be used as an indicator of level of global mental distress. A weighted sum of 5 questions from the Symptom Check List (SCL) anxiety and depression subscales (SCL-25) correlates at r = 0.92 with the global SCL-25 score. The alpha reliability for the (5-item) short form questionnaire was 0.85%. Age differences seemed to be trivial, and sex differences were moderate. Descriptive statistics for short form scores in a large, representative sample are given.

Adult↗

PubMed1993

Age-specific genetic effects for blood pressure.

Correlations between relatives were determined for systolic and diastolic blood pressure. The correlations decrease as age differences between relatives increase in a Norwegian sample with 43,751 parent-offspring pairs, 19,140 pairs of siblings, and 169 pairs of twins. A simple biometric model specifying only age-specific genetic additive effects and environmental effects fitted well to correlations between cotwins, pairs of siblings, and parent-offspring dyads in subsets of relatives grouped by age differences. None of the environmental effects appeared to be due to environmental factors that are shared by family members. Models that excluded a parameter for the age-specific genetic influence did not fit the data. The results may partly explain what seems to be a discrepancy between relatively low parent-offspring correlations from previous nuclear family studies and high correlations from twin studies, especially in identical twins.

Adult↗

PubMed1992

Genetic and environmental contributions to the variance of body height in a sample of first and second degree relatives.

Height was measured in a health screening of the population in Nord-Trøndelag, Norway. Correlations were computed for 24,281 pairs of spouses, 43,613 pairs of parents and offspring, 19,168 pairs of siblings, 1,318 pairs of grandparents and grandchildren, 1,218 cognate avuncular pairs, 849 noncognate avuncular pairs, 175 pairs of same-sexed twins, and smaller groups of other types of relatives. Fitting of structural equation models showed proportions of additive genetic variance of approximately 0.8 for both sexes and small sex-specific effects that probably reflect genetic dominance or environmental sibling effects. The correlations between parents and offspring were significantly lower in old than young cohorts, seeming to imply some kind of interaction effect between genes and environment.

Age Factors↗

PubMed1992

Genetic and environmental effects on blood pressure in a Norwegian sample.

Systolic (SBP) and diastolic (DBP) blood pressures were measured in a health screening of the adult population in Nord-Trøndelag, Norway. Correlations were computed for 23,936 pairs of spouses, 43,586 pairs of parent and offspring, 19,151 pairs of siblings, 1,251 pairs of grandparents-grandchildren, 1,146 pairs of biological uncles/aunts-nephews/nieces (avuncular), 801 non-biological avuncular pairs, 169 pairs of same-sex twins, and smaller groups of other types of relationships. Spouse correlations of 0.08 and 0.09 were approximately constant or slightly decreasing with marital duration. The correlation values for SBP and DBP were approximately 0.16 for parents-offspring, 0.19 to 0.23 for same-sex siblings with similar values for DZ twins, 0.19 and 0.16 for opposite-sex siblings, 0.52 and 0.43 for MZ twins, and close to zero for most of the second-order relationships. Genetic additive variance was estimated at 0.29 and genetic dominance variance at 0.18 with the best model for SBP. The corresponding estimates from the best models for DBP were 0.29 or lower and 0.22 or lower, the sum not exceeding 0.35. There was evidence of a moderate effect of environmental factors shared by same-sex siblings and twins (for DBP), but no cultural transmission, and whether or not adult relatives live together does not affect familial resemblance for BP. The data did not permit a very precise resolution of the relative magnitude of genetic dominance and sibling effects. The correlation structure did not show sex-specific genetic effects.

Adult↗

PubMed1992

Genetic and environmental effects on type A scores in monozygotic twin families.

Monozygotic (MZ) twin pairs with spouses and children, altogether 787 subjects, completed the Jenkins Activity Survey (JAS). The observed correlations for the various sets of relationships fitted well with biometric models including only parameters for additive genetic effects and, for Type A and Job Involvement, assortative mating. There was no evidence of effects of the family environment (cultural transmission) or genetic dominance (nonadditivity). For all but the Hard Driving and Competitive scale, there was evidence of effects of sex-specific genes. The heritability estimates were, for males and females, respectively, .33 and .39 for Type A, .36 and .48 for Job Involvement, .20 and .52 for Speed and Impatience, and .13 (both sexes) for Hard Driving and Competitive. The estimates given here are deflated by measurement errors and should probably be corrected by multiplying by values in the neighborhood of 1.3. Even after correction, the results suggest that individual differences for Type A and related traits depend more on nonfamilial environment than on genes.

Adult↗