Genetic and Environmental Influences on Disability Pension Due To Mental Diagnoses: Limited Importance of Major Depression, Generalized Anxiety, and Chronic Fatigue

Genetic and environmental contributions to individual differences in sustainable working life-A Swedish twin cohort study

Although genetics is known to have a role in sickness absences (SA), disability pensions (DP) and in their mutual associations, the empirical knowledge is scarce on not having these interruptions, i.e., sustainable working life. Hence, we aimed to investigate how genetic and environmental factors affect individual variation in sustainable working life in short-term (two consecutive years) and in long-term (22 years of follow-up) using the classical twin modeling based on different genetic relatedness of mono- and dizygotic twins. The final sample (n = 51 071) included Swedish same-sex twins with known zygosity born between 1930 and 1990 (53% women) with complete national register data of employment, SA, DP, unemployment, old-age pension, emigration, and death. For the short-term sustainable working life, genetic factors explained 36% (95% confidence intervals (CI) 31-41%), environmental factors shared by co-twins such as family background 8% (95% CI 5-14%) and environmental factors unique to each twin individual 56% (95% CI 56-56%) on the individual differences. For the long-term sustainable working life, the largest proportions on individual differences were explained by environmental factors shared by co-twins (46%, 95% CI 44-48%) and unique to each twin individual (37% 95% CI 36-38%) whereas a small proportion was explained by genetic factors (18%, 95%CI 14-22%). To conclude, short-term sustainable working life was explained to a large extent by unique environment and to lesser extent by genetic factors whereas long-term (22 years) sustainable working life had both moderate unique and common environmental effect, and to lower extent genetic effects contributing to individual differences. These findings suggest that sustainable working life have different short- and long-term predictors.

Sickness absence transitions among Swedish twins with back, neck or shoulder pain and common mental disorders applying a multi-state approach

We aimed to investigate transitions to and from sickness absence, or disability pension among individuals with back, neck, or shoulder pain and/or with common mental disorders (CMDs), and the role of familial (genetics and shared environment) influences on the transitions. Swedish twins born 1935-1985 who responded to pain and CMDs survey items (N = 41,516) were followed on average 8.7 years for sickness absence states in national registers. Multi-state Cox regression models were applied for three exposure groups: pain, CMDs, and presence of both, compared to unexposed. Exposure discordant twin pairs, stratified by zygosity, were analysed to assess the role of familial factors. Hazard Ratios (HR) with 95% confidence intervals and transition intensities were calculated. HRs were similar for transitions between states among those with pain or CMDs. The highest HRs were for transitions from entry to sickness absence and sickness absence to disability pension among those with both pain and CMDs (HRs: 1.61 and 1.43, respectively). Higher HRs for dizygotic compared to monozygotic twins for the first transition to sickness absence and for altering back to not being sickness absent indicate familial confounding. Back, neck, or shoulder pain and/or CMDs indicate a higher risk to become sickness absent and for repeated sickness absence episodes over time compared to unaffected.

Sickness absence among young employees in private and public sectors with a history of depression and anxiety

The aim was to investigate occurrence and duration of sickness absence (SA) among young employees with previous depression/anxiety in private and public sectors. This population-based prospective study included 11,519 Swedish twin individuals of age 19-29 years that were followed regarding SA during 2006-2016. Data on previous depression/anxiety came from two screening surveys in 2005. Data on SA and employment sector were received from national registries. Descriptive statistics and logistic regression were used, also controlling for familial factors. Proportion of employees with SA was significantly higher among those with, as compared to those without, previous depression/anxiety, regardless the employment sector. Individuals with previous depression/anxiety had increased risk for future SA, in both private (OR 2.25, 95% CI 1.90-2.66) and public sectors (OR 2.10, 95% CI 1.73-2.54). Familial factors played a role in the association among employees in the private sector. A higher proportion of long-term SA was observed among employees with previous depression/anxiety in the private as compared to the public sector. To conclude, previous depression/anxiety tends to increase risk for SA among young employees in both employment sectors, whereas long-term SA seemed to be more prevalent among those in the private as compared to the public sector.

Sustainable Working Life in a Swedish Twin Cohort-A Definition Paper with Sample Overview

Background: A unified or consensus definition of “sustainable working life” remains lacking, although studies investigating risk factors for labour market exit are numerous. In this study, we aimed (1) to update the information and to explore a definition of “sustainable working life” via a systematic literature review and (2) to describe the working life trajectories via the prevalence of sickness absence (SA), disability pension (DP), and unemployment in a Swedish twin cohort to provide a sample overview in our Sustainable Working Life-project. Methods: A systematic literature review was conducted to explore the studies with the search phrase “sustainable working life” in PubMed, PsycInfo, and the Web of Science Database of Social Sciences in January 2021, resulting in a total of 51 references. A qualitative synthesis was performed for the definitions and the measures of “sustainable working life.” Based on the Swedish Twin project Of Disability pension and Sickness absence (STODS), the current dataset to address sustainable working life includes 108 280 twin individuals born between 1925 and 1990. Comprehensive register data until 2016 for unemployment, SA and DP were linked to all individuals. Using STODS, we analysed the annual prevalence of SA, DP, and unemployment as working life trajectories over time across education and age groups. Results: The reviewed 16 full articles described several distinct definitions for sustainable working life between 2007 and 2020 from various perspectives, i.e., considering workplaces or employees, the individual, organizational or enterprise level, and the society level. The definition of “sustainable working life” appearing most often was the swAge-model including a broad range of factors, e.g., health, physical/mental/psychosocial work environment, work motivation/satisfaction, and the family situation and leisure activities. Our dataset comprised of 81%–94% of individuals who did not meet SA, DP, or unemployment during the follow-up in 1994–2016, being indicative for “sustainable working life.” The annual prevalence across years had a decreasing trend of unemployment over time, whereas the prevalence of SA had more variation, with DP being rather stable. Both unemployment and DP had the highest prevalence among those with a lower level of education, whereas in SA, the differences in prevalence between education levels were minor. Unemployment was highest across the years in the youngest age group (18–27 years), the age group differences for SA were minor, and for DP, the oldest age group (58–65 years) had the highest prevalence. Conclusions: No consensus exists for a “sustainable working life,” hence meriting further studies, and we intend to contribute by utilising the STODS database for the Sustainable Working Life project. In the upcoming studies, the existing knowledge of available definitions and frameworks will be utilised. The dataset containing both register data and self-reports enables detailed follow-up for labour market participation for sustainable working life.

Shared liability to pain, common mental disorders, and long-term work disability differs among women and men

Knowledge of factors involved in the associations between pain, common mental disorders, and future work incapacity is still scarce. The aim of this study was to examine the overlap between genetic and environmental factors contributing to depression/anxiety, pain, and future long-term sickness absence (SA) and disability pension (DP) among women and men. The study sample included 47,995 twins born in Sweden 1935 to 1985. Information on self-reported depression/anxiety and back, neck, and shoulder pain was obtained from surveys conducted 1998 to 2002 and 2004 to 2005. Data on long-term SA (>365 days) and DP due to mental and/or musculoskeletal disorders until 2013 were obtained from the National Social Insurance Agency. Shared genetic and environmental influences on depression/anxiety, pain, and SA/DP were estimated by applying structural equation modeling. The prevalence of depression/anxiety was 27% and 14% among women and men, for pain 24% and 19%, and for SA/DP due to mental and musculoskeletal diagnoses 7% and 4%, respectively. Multivariate biometric analyses revealed different patterns of covariation between the 3 phenotypes among women and men. For women, a latent-shared liability to all 3 phenotypes could be identified, mainly attributable to genetic factors (66%). For men, no shared underlying liability was observed. The variation in SA/DP was explained by genetic factors in common with depression/anxiety by 27% and in common with pain by 9%. Common mental disorders, pain, and SA/DP tend to covariate in different ways among women and men. The results may have clinical implications as strategies preventing SA/DP may be different among women and men.

Number of Pain Locations as a Predictor of Cause-Specific Disability Pension in Sweden-Do Common Mental Disorders Play a Role?

OBJECTIVE

The aim of this study was to investigate the associations between number of pain locations, common mental disorders (CMDs), and disability pension (DP).

METHODS

Survey data in 1998 to 2003 for 27,165 Swedish twins born in 1935 to 1958 were linked to national DP data until 2013. Pain locations were evaluated for back, low back, sciatica, shoulder, or neck pain, and CMDs for lifetime major depression and 1-month anxiety.

RESULTS

The number of pain locations was associated with DP in a dose-response manner. One pain location had a hazard ratio of 1.50 (95% confidence interval 1.35 to 1.68) and five pain locations hazard ratio 4.67 (95% confidence interval 4.11 to 5.30) for DP. Also, CMDs were associated with DP.

CONCLUSION

The number of pain locations has a dose-response association with the risk of DP. CMDs predict DP. In strategies to prevent DP, early signs of pain or CMDs should be taken into consideration.

Sick leave due to back pain, common mental disorders and disability pension: Common genetic liability

BACKGROUND

Back pain and common mental disorders are often comorbid and known risk factors for future disability pension. However, the reason for the covariation is not known. The aim was to investigate the common genetic and environmental influences on the covariation between sick leave due to back pain, sick leave due to common mental disorders and disability pension.

METHODS

Register data from the Swedish Social Insurance Agency on sick leave due to back pain, common mental disorders and disability pension between 2005 and 2018, in a population-based sample of 56,686 working age twins was used to construct biometric twin models to calculate if the covariation between the traits were due to Additive (A) or Dominant (D) genetic factors, Common environmental factors (C) or unique Environmental factors (E), for women and men.

RESULTS

The phenotypic correlations ranged between 0.17 and 0.25. A common factor common pathway AE model fitted best for both women and men. The latent underlying common factor, that explained the covariation was mostly explained by genetic factors (87% for women and 90% for men). Each trait was also influenced by its own unique genetic and unique environment factors. A higher heritability was found for disability pension than for sick leave.

CONCLUSIONS

The covariation between sick leave due to back pain and common mental disorders, and disability pension were mostly explained by common genetic factors, while the unique variation in each trait was influenced by both genetic and environmental factors not shared within the twin pairs.

SIGNIFICANCE

A common genetic liability seems to be of importance in the comorbidity of sick leave due to back pain and common mental disorders and the transition to disability pension, both among women and men. However, the proportion in each trait that was explained by genetic factors was somewhat higher for men than for women in all traits. This may be of importance to consider in intervention or prevention efforts.

The longitudinal integrated database for health insurance and labour market studies (LISA) and its use in medical research

Education, income, and occupation are factors known to affect health and disease. In this review we describe the Swedish Longitudinal Integrated Database for Health Insurance and Labour Market Studies (LISA, Longitudinell Integrationsdatabas för Sjukförsäkrings- och Arbetsmarknadsstudier). LISA covers the adult Swedish population aged ≥ 16 years registered on December 31 each year since 1990 (since 2010 individuals aged ≥ 15 years). The database was launched in response to rising levels of sick leave in the country. Participation in Swedish government-administered registers such as LISA is compulsory, and hence selection bias is minimized. The LISA database allows researchers to identify individuals who do not work because of injury, disease, or rehabilitation. It contains data on sick leave and disability pension based on calendar year. LISA also includes information on unemployment benefits, disposable income, social welfare payments, civil status, and migration. During 2000–2017, an average of 97,000 individuals immigrated to Sweden each year. This corresponds to about 1% of the Swedish population (10 million people in 2017). Data on occupation have a completeness of 95%. Income data consist primarily of income from employment, capital, and allowances, including parental allowance. In Sweden, work force participation is around 80% (2017: overall: 79.1%; men 80.3% and women 77.9%). Education data are available in > 98% of all individuals aged 25–64 years, with an estimated accuracy for highest attained level of education of 85%. Some information on civil status, income, education, and employment before 1990 can be obtained through the Population and Housing Census data (FoB, Folk- och bostadsräkningen).

Familiality and Heritability of Fatigue in an Australian Twin Sample

Familial factors have previously been implicated in the etiology of fatigue, of which a significant proportion is likely attributable to genetic influences. However, family studies have primarily focused on chronic fatigue syndrome, while univariate twin studies have investigated broader fatigue phenotypes. The results for similar fatigue phenotypes vary between studies, particularly with regard to sex-specific contributions to the heritability of the traits. Therefore, the current study aims to investigate the familiality and sex-specific effects of fatigue experienced over the past few weeks in an older Australian population of 660 monozygotic (MZ) twin pairs, 190 MZ singleton twins, 593 dizygotic (DZ) twin pairs, and 365 DZ singleton twins. Higher risks for fatigue were observed in MZ compared to DZ co-twins of probands with fatigue. Univariate heritability analyses indicated fatigue has a significant genetic component, with a heritability (h2) estimate of 40%. Sex-specific effects did not significantly contribute to the heritability of fatigue, with similar estimates for males (h2= 41%, 95% CI [18, 62]) and females (h2= 40%, 95% CI [27, 52]). These results indicate that fatigue experienced over the past few weeks has a familial contribution, with additive genetic factors playing an important role in its etiology.