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Biomedical subjects

J M Sundet

Publications and source records attributed to J M Sundet.

16 recordsLinked to original sources
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↗
PubMed1992

Secular trends and sociodemographic regularities of coital debut age in Norway.

Gender and birth cohort differences and the influence of social background variables on the coital debut age were investigated in the general population of Norway. The data derive from a 1987 questionnaire on sexual behavior mailed to a random sample of 10,000 Norwegians of both sexes, ages 18 through 60; 63% responded to the questionnaire. 94.5% reported that they had experienced intercourse. The median coital debut age was 18.2 years. There were both cohort and gender differences. Younger cohorts have lower coital debut ages, and women younger than 35 years experienced their first intercourse at an earlier age than men in the same age group. When each independent variable was analyzed separately, there were substantial differences between educational levels and social classes with respect to age of coital debut. Multivariate analysis of six separate cohorts revealed independent effects of gender in the two youngest cohorts, whereas educational level had significant independent effects in all but the oldest cohort. Social class did not reveal any independent effect on coital debut age. Population density of the place of residence of the respondents was not substantially related to age of coital debut. Seen together, the independent variables explain about 13% of the variance in coital debut age (by multiple regression).

Adolescent↗
PubMed1992

Use of birth control pills and condoms among 17-19-year-old adolescents in Norway: contraceptive versus protective behaviour?

This article addresses the relationship between sexual risk behaviour and contraceptive behaviour, and considers whether adolescents who use condoms are practising birth control or STD protective behaviour. The material comprised a representative sample of 3000 Norwegians aged 17-19 years. Data were collected by anonymous self-administered questionnaires. The response-rate was 63%. At the first sexual intercourse 51% of the adolescents used condoms and 7% birth control pills. At the most recent intercourse 31% used condoms and 38% the pill. Use of the pill was widespread among adolescents with high coital frequency and few coital partners. Use of condoms was not particularly widespread among adolescents who reported a relatively large number of coital partners. Irrespective of the number of years they had been coitally active there was no significant difference between those who intended to use condoms at the next sexual intercourse and those who did not as regards their beliefs about condoms as protection against STDs, HIV and unintended pregnancies. The results from this study indicate that the majority of adolescents who use contraception do this for protection against unintended pregnancy and not for protection against STDs. The preference for the pill may make teenagers less prepared to practise STD protective behaviour in specific situations.

Acquired Immunodeficiency Syndrome↗
PubMed1991

The potential for spread of HIV in the heterosexual population in Norway: a model study.

A simulation model is used to investigate the potential for indigenous spread of human immunodeficiency virus (HIV) in the heterosexual population in Norway. The heterosexual population is grouped according to age, sex and whether paired or single. Estimates of various parameters of sexual behaviour are taken from a population-based questionnaire study. The questionnaire was sent to a random sample of 10,000 individuals, with a response rate of 63 per cent. The main simulation result is that with no inflow of infection from other risk groups, the heterosexual epidemic will decline if the average transmission probability per intercourse is 1 per cent or less. This result is insensitive to changes in the initial conditions. It is sensitive to changes in sexual behaviour, and to the shape of the transmission probability distribution. A review of empirical partner study data indicates an average transmission probability about 0.1 per cent per intercourse when no transmission modulating cofactors are present. It is concluded that with present sexual behaviour, the indigenous spread of HIV is not likely to sustain an epidemic in the Norwegian heterosexual population.

Adult↗
PubMed1991

Pedigree analysis of Eysenck Personality Questionnaire (EPQ) scores in monozygotic (MZ) twin families.

MZ twins with spouses and children, altogether 811 subjects, completed the Eysenck Personality Questionnaire (EPQ). For extraversion (E), neuroticism (N), and lying (L), models including only additive genetic effects fitted well to the observed sex-specific correlations for the various sets of relationships. There was no evidence of sex differences for any parameter estimate for E, N, and L. The fit for E improved significantly after including dominance, and the fit for L improved significantly after including assortative mating. A model specifying genetic additive and dominance effects and assortative mating fitted well to the Psychoticism (P) data, but the fit improved significantly when a parameter for cultural transmission from fathers to daughters were included. Except for this, there was no evidence of cultural transmission for any scores. The heritabilities for the best-fitting models were .53 (E), .36 (N), .43 (L), and .39 (P). The latter includes almost only nonadditive, and no additive, variance, suggesting an overestimation of this effect due to random fluctuation or environmental sibling effect misinterpreted as dominance.

Adult↗
PubMed1990

[Attitude towards use of condoms among Norwegian adolescents].

The article discusses the relationship between attitudes towards condoms and the use of condoms among sexually active Norwegian adolescents. The data stem from a random survey of 3,000 Norwegian adolescents aged 17-19. The responsrate was 61.8%. In general, most adolescents were positive towards condoms, and condom users were more positive than non-users. A logistic regression analysis showed that the only statistically significant predictors of condom use were the attitudes 'condoms aren't necessary to me' and 'condoms are uncomfortable'. The results indicate that attitudes towards condoms bear some relation to condom use. But, the use of condoms is also governed by factors other than attitudes.

Adolescent↗
PubMed1989

[Use of condoms in relation to risk behavior among the heterosexual population in Norway].

In a questionnaire survey on sexual behaviour, a random sample of 10,000 Norwegians aged 18 through 60 were asked about use of condoms during their last intercourse. The response rate was 62.7%. Except as regards level of education, the response group was fairly representative of the population with respect to socio-demographic variables. About 12% reported use of condom. Among subjects who reported extra-marital partners, about 7% used condoms (both with their permanent and their extra-marital partner), whereas about 12% of subjects who did not have extramarital sex used condoms. 15% of the single persons reported use of condom. Apparently, the use of condoms is not related to sexual behaviour correlated with risk of HIV-infection, such as the number of partners and knowledge about the partner. Neither is perceived risk, as measured by HIV-testing behaviour, related to the use of condoms.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Genetic and environmental contributions to the covariance between occupational status, educational attainment, and IQ: a study of twins.

Scores of occupational status, educational attainment, and IQ were obtained for 507 monozygotic and 575 dizygotic male twin pairs born 1931-1935 and 1944-1960. A multivariate genetic analysis with statistics from different cohorts showed heterogeneity between cohorts, and analyses were performed in four separate cohorts. The only set of results which departed clearly from the rest was found for the group born 1931-1935, where the ratio of environmental to genetic effects exceeded those of the other groups. Typical heritability values in the three youngest groups (weighted means) were .43, .51, and .66 for occupation, education, and IQ, respectively. The values in the oldest group were .16, .10, and .37, but this sample is small and the estimates are unstable. Genetic variance influencing educational attainment also contributed approximately one-fourth of the genetic variance for occupational status and nearly half the genetic variance for IQ. The values for the between-families variances (reflecting family environment and assortative mating) varied from 2 to 35% in the three youngest groups but were higher for education (62%) and IQ (45%) in the oldest groups. All the between-families variance was common to all three variables. For educational attainment and IQ, the bulk of this between-families variance is probably genetic variance due to assortative mating. The common-factor environmental within-family variances were generally small, and the specific estimates seemed to contain mainly measurement error.

Achievement↗
PubMed1985

Cotwin closeness in monozygotic and dizygotic twins: a biasing factor in IQ heritability analysis?

For 98 pairs of MZ twins, four measures indicating degree of cotwin closeness were correlated with absolute differences between IQ scores within pairs. In two different twin samples (40 MZ vs 40 DZ pairs and 169 MZ vs 174 DZ pairs, respectively), means and standard deviations in the closeness variables were obtained for MZ and DZ pairs. Whereas MZ cotwins were clearly closer than DZ cotwins, the relation between cotwin closeness and similarity in IQ seemed rather weak and ambiguous. "Years lived together in childhood home" were positively related to similarity in IQ (P less than 0.01), whereas subjective feeling of closeness in contact tended to be negatively related to similarity in IQ.

Adult↗