38 research outputs found
Maternal body composition in relation to twinning
Monozygotic (MZ) twinning is considered to be a random event whereas spontaneous dizygotic (DZ)
twinning is influenced by several factors. Thus, secular changes in twinning rates are usually explained by
changes in DZ twinning alone. Maternal body mass index (BMI) before pregnancy and maternal height are
believed to be significant drivers of twinning. Our aim in this study was to explore to what degree maternal
body composition influences twinning. Data on births and maternal height and BMI from the Medical Birth
Registry Norway (MBRN) was analyzed applying multivariate logistic regression analysis. The results
showed that increasing maternal BMI and height has a positive association with twinning. There is an
increased risk of DZ twinning for a maternal BMI > 25, OR 1.31-1.43 and for maternal height ≥ 173 cm,
OR 1.28. In explaining secul
Health problems account for a small part of the association between socioeconomic status and disability pension award. Results from the Hordaland Health Study
<p>Abstract</p> <p>Background</p> <p>Low socioeconomic status is a known risk factor for disability pension, and is also associated with health problems. To what degree health problems can explain the increased risk of disability pension award associated with low socioeconomic status is not known.</p> <p>Methods</p> <p>Information on 15,067 participants in the Hordaland Health Study was linked to a comprehensive national registry on disability pension awards. Level of education was used as a proxy for socioeconomic status. Logistic regression analyses were employed to examine the association between socioeconomic status and rates of disability pension award, before and after adjusting for a wide range of somatic and mental health factors. The proportion of the difference in disability pension between socioeconomic groups explained by health was then calculated.</p> <p>Results</p> <p>Unadjusted odds ratios for disability pension was 4.60 (95% CI: 3.34-6.33) for the group with elementary school only (9 years of education) and 2.03 (95% CI 1.49-2.77) for the group with high school (12 years of education) when compared to the group with higher education (more than 12 years). When adjusting for somatic and mental health, odds ratios were reduced to 3.87 (2.73-5.47) and 1.81 (1.31-2.52). This corresponds to health explaining only a marginal proportion of the increased level of disability pension in the groups with lower socioeconomic status.</p> <p>Conclusion</p> <p>There is a socioeconomic gradient in disability pension similar to the well known socioeconomic gradient in health. However, health accounts for little of the socioeconomic gradient in disability pension. Future studies of socioeconomic gradients in disability pension should focus on explanatory factors beyond health.</p
Social inequalities in reception of social welfare support: A population based twin study
Social welfare support runs in families. Recent studies using Nordic registry data have found individual
differences in genetic factors to be of substantial importance for medical benefits. However, to date there has
been no genetically informative studies on receiving social welfare support. To prevent young adults to not
drop out of the work life and become recipients of social welfare support, it is of substantial interest to
clarify to what extent the familiarity of social welfare support is due to genetic or social differences between
families. We used data from the Historical-Event Database on 7,698 Norwegian twins born 1967-1979 to
estimate the relative contribution of genetic factors, the effective familial environment (i.e. the “shared
environment”), and individual-specific environmental factors. We found that the two forms of familial risk,
genetic and shared environmental, explained 39% and 45%, respectively, of the risk for receiving social
welfare support among young Norwegian twins. Only 17% of the variance in risk factors could be explained
by individual-specific risk factors. It appears that risk for receiving social welfare support can to a great
extent be explained by environmental differences between families. Therefore prevention strategies targeting
social inequalities between families would indeed be effective. Furthermore, genetic risk factors are also
important in explaining risk for receiving social welfare support. These effects could be mediated through
heritable traits related to substance abuse, psychiatric disorders, and personality. Individual-specific risk factors
were of very little importance. Hence, with regard to receiving social welfare support, family matters
Socioeconomic status and sick leave granted for mental and somatic disorders: a prospective study of young adult twins
Background Low socioeconomic status (SES), indicated by low income and education, has consistently been found to be a strong predictor of sick leave. Several possible pathways from SES to sick leave have been described in previous literature, but there are also evidence indicating that the association can be confounded by common underlying factors. This study utilizes a population-based sample of employed young adult twins to estimate (i) the degree to which education and income are prospectively related to sick leave granted for mental, somatic, and any disorder, and (ii) whether these associations are confounded by familial factors.
Methods Registry data on educational attainment and income at age 30 and subsequent sick leave were available for 6,103 employed young adult twins, among which there were 2,024 complete twin pairs. The average follow-up time was 6.57 years. Individual-level associations and fixed effects within twin pairs were estimated.
Results Low education and income were associated with sick leave granted for both mental and somatic disorders, and with sick leave granted for any disorder. Associations were attenuated within dizygotic twin pairs and reduced to non-significance within monozygotic twin pairs, suggesting influence of familial factors on the associations between SES and sick leave.
Conclusions Low SES is associated with a higher level of sick leave granted for both mental and somatic disorders among young adults, but these associations are confounded by factors that are common to co-twins. Education and income are therefore not likely to strongly affect sick leave in young adulthood
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Advantages of linking national registries with twin registries for epidemiological research
Linking national registries with twin data represents an opportunity to produce epidemiological research of
high quality. National registries contain information on a broad array of variables, some of which cannot be
measured reliably in regular health surveys. By taking kinship into consideration, twin studies have the
benefit of being able to identify confounding stemming from genetic or shared environmental sources. In
this paper, we use examples from our own interview and questionnaire-based twin studies from the Norwegian
Twin Registry (NTR) on mental disorders, alcohol use and socioeconomic status linked to registry
data on medical benefits to demonstrate the value. In the first example, we examined to what extent genetic
and environmental factors contributed to sick leave and disability pension and the association between these
two types of benefits. In the second example, we explored the genetic and environmental relationship
between personality disorders and sick leave. In the third example, a co-twin control design was applied to
explore whether there is a true protective relationship between moderate alcohol consumption and health.
The fourth example shows to what degree anxiety and depression are associated with later sick leave granted
for not only mental disorders, but also somatic disorders, adjusted for confounding by genetic and shared
environmental factors. In the fifth example, we address the socioeconomic gradient in sick leave, adjusting
for non-observed confounders associated with the family in a co-twin control design. Our examples illustrate
some of the potentials obtainable by linking national registries with twin data. The efforts that have been
made to create the NTR in Norway and the International Network of Twin Studies (INTR) internationally
make these types of linkage studies easier to conduct and available to more researchers. As there are still
many areas to explore, we encourage epidemiological researchers to make use of this possibility
Musculoskeletal pain and work absence – a 10 year follow-up study of Norwegian young adult twins
Background and aims: Sickness absence (SA) and disability pension (DP) are increasingly recognized as
major public problems. Musculoskeletal disorders are among the most common diagnoses set by physicians
granting SA and DP. Results from recent twin studies have established that SA and DP are influenced
not only by environmental and social factors, but also moderately to substantially by genes. The aim of the
current study was to examine to what degree musculoskeletal complaints in young adults predict SA and
DP, including SA granted for other diagnoses. As the participants were twins, we were able to perform
within pair analyses, to see if the associations between musculoskeletal pain and later DP or SA were confounded
by unmeasured genetic and shared environmental factors.
Materials and methods: The Norwegian twin registry includes a questionnaire conducted in 1998. From
this, we included three measures of recurrent pain (lower back, neck/shoulders and muscular) as well as
symptoms of anxiety and depression (measured by the Symptom Checklist-5 (SCL-5)). The questionnaire
has been linked to highly reliable official registries on SA and DP, as well as a range of sociodemographic
variables, for a ten-year follow up period. We applied logistic (DP as dependent variable) and binomial
regression (SA as dependent variable) analyses to explore the relationship between musculoskeletal pain
and DP and SA. In the final models, we adjusted for sociodemographic factors and symptoms of anxiety
and depression. Differences between twins in a pair were explored by applying fixed effect models. All
analyses were conducted using STATA version 13.1.
Results: The final sample of 7,626 twins included 3,055 complete pairs (488 monozygotic (MZ) male, 349
dizygotic (DZ) male, 747 MZ female, 589 DZ female, and 882 opposite sex twin pairs) and 1,516 singletons.
By the end of follow up, 181 subjects (44 men and 137 women) received DP, and 63.7% of the sample
(47.4% of males and 76.0% of females) had at least one period of SA extending 16 days. Pain at any site
was significantly associated with DP in both sexes. Any increase in the number of pain sites reported was
associated with about a 60% increased risk for receiving DP (OR 1.6, 95% CI 1.4-1.9), and the strength of
the association was only marginally reduced when adjusted for symptoms of mental disorders (1.4, 1.2-
1.7). In the within pair analyses the effect was no longer significant, indicating possible confounding from
genetic and shared environmental effects. As for all cause SA, musculoskeletal pain predicted SA independently
of all measured confounders, and the results remained significant in the within pair analyses (Incidence
Rate Ratio (IRR) 1.12, 95% CI 1.03-1.23).
Conclusion: In young adults, musculoskeletal pain strongly predicted SA and DP for a 10 year follow-up
period. Musculoskeletal pain was associated with higher levels of all cause SA, even within discordant MZ
twin pairs. Our results indicate that interventions to prevent musculoskeletal pain in young adults can
reduce levels of SA and DP
The Norwegian Twin Registry
The Norwegian Twin Registry (NTR) is a large population based twin cohort for research purposes. At present,
the registry has 14 692 complete twin pairs with information on zygosity and to varying degree information on
somatic and mental health, lifestyle and demographics. The registry covers birth years 1895-1960 and 1967-
1991. NTR was established in 2009, at the Norwegian Institute of Public Health, as a merger of three major
twin panels, the oldest originating in the 1960s. Since then Norwegian twin research has been a notable
contributor to twin research internationally. Norwegian twin researchers have published over 250 papers based
on Norwegian twin data, spanning a broad range of somatic and mental health phenotypes. In twin studies of
heritability a data structure with both variance within and between pairs is required. Therefore a large sample is
necessary, especially when studying rare diseases and conditions, and it is of vital importance to expand the
registry. NTR is actively recruiting new twins, both young and older, but declining response rates are a
challenge. The value of NTR is greatly enhanced through the linkage possibilities offered by Norway’s many
nationwide registries (medical, demographic, and socio-economic). Access to data is permitted by the NTR
steering group and will in most instances need permission from the Regional Ethics Committee