A Life Course Study of Genetic and Environmental Influences on Work Incapacity

The role of familial factors and neuroticism in the association between exposure to offensive behaviors at work and long-term sickness absence due to common mental disorders - a prospective twin study

OBJECTIVES

The aim of this study was to investigate associations between exposure to work-related violence/threats and harassment, and future sickness absence (SA) due to common mental disorders (CMDs), taking familial factors (shared genetics and early-life environment) and neuroticism into account.

METHODS

The study sample included 8795 twin individuals from the Swedish Twin Project of Disability Pension and Sickness Absence (STODS), including survey data from the Study of Twin Adults: Genes and Environment (STAGE). Self-reported work-related violence and/or threats as well as work-related harassment (including bullying) and national register data on SA due to CMDs were analyzed using standard logistic regression, and conditional logistic regression among complete twin pairs discordant on exposures. Individuals were followed for a maximum of 13 years. Interactions between neuroticism and exposures were assessed using both multiplicative and additive interaction analyses.

RESULTS

Exposure to work-related violence/threats was associated with higher odds of SA due to CMDs when adjusting for age, sex, marital status, children, education, type of living area, work characteristics, and symptoms of depression and burnout (OR 2.11, 95% CI 1.52-2.95). Higher odds of SA due to CMDs were also found for exposure to harassment (OR 1.52, 95% CI 1.10-2.11) and a combined indicator of exposure to violence/threats and/or harassment (OR 1.98, 95% CI 1.52-2.59), compared with the unexposed. Analyses of twins discordant on exposure, using the unexposed co-twin as reference, showed reduced ORs. These ORs were still elevated but no longer statistically significant, potentially due to a lack of statistical power. No multiplicative interaction was found between neuroticism and exposure to work-related violence/threats, or harassment. However, a statistically significant additive interaction was found between neuroticism and exposure to violence/threats, indicating higher odds of SA due to CMDs in the group scoring lower on neuroticism.

CONCLUSIONS

Exposure to work-related offensive behaviors was associated with SA due to CMDs. However, the results indicated that these associations may be partly confounded by familial factors. In addition, an interaction between exposure and neuroticism was suggested. Thus, when possible, future studies investigating associations and causality between offensive behaviors at work and mental health-related outcomes, should consider familial factors and neuroticism.

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.

Work incapacity and psychiatric patient care following attempted suicide - a cohort study of 65 097 Swedish twins

BACKGROUND

Research is scarce on the role of familial factors and previous psychiatric care on the association between suicide attempt and future work incapacity as well as deterioration in mental health. We aimed to investigate the associations between suicide attempt and sickness absence, disability pension and psychiatric patient care and to study the influence of previous psychiatric care and familial factors (genetics and shared environment) on the associations.

METHODS

The study included 65 097 twins living in Sweden on 31st of December 2006, aged 19-60 years. The twins were followed 2007-2013 regarding sickness absence, disability pension, inpatient care or specialized outpatient care for a mental diagnosis. Cox regression models were performed for the whole sample, and conditional models for discordant twin pairs. The analyses were also stratified by psychiatric care before 2007.

RESULTS

We found that suicide attempt predicted sickness absence, disability pension, and future mental diagnosis among the whole sample. The discordant twin pair analyses showed that the association between suicide attempt and sickness absence or disability pension was influenced by familial factors. Stratified analyses of individuals with or without psychiatric care before 2007 showed that previous psychiatric care had some impact on the associations.

CONCLUSIONS

A suicide attempt is a risk factor for work incapacity and psychiatric patient care. Familial factors and previous psychiatric care play a role in the associations between attempting suicide and work incapacity as well as psychiatric patient care. These factors are important when developing measures preventing work incapacity among those with a suicide attempt.

Associations of Internalizing and Externalizing Problems in Childhood and Adolescence With Adult Labor Market Marginalization

Importance

Mental health problems in early life are associated with labor market marginalization, especially in youths with persistent internalizing and externalizing problems. However, previous research has not adjusted for familial (genetic and shared environmental) factors.

Objective

To examine associations of early-life internalizing and externalizing problems with adulthood unemployment and work disability, adjusting for familial factors.

Design, Setting, and Participants

This population-based prospective cohort study included Swedish twins who were born in 1985-1986 and surveyed at 4 consecutive waves across childhood and adolescence until 2005. Through linkage to nationwide registries, participants were followed up from 2006 to 2018. Data analyses were conducted between September 2022 and April 2023.

Exposures

Internalizing and externalizing problems, assessed with the Child Behavior Checklist. Participants were differentiated regarding duration of internalizing and externalizing problems (persistent, episodic, and noncases).

Main Outcomes and Measures

Unemployment (180 days or more of being unemployed) and work disability (60 days or more of being sickness absent or disability pensioned) during follow-up. Cox proportional hazards regression models were calculated to obtain cause-specific hazard ratios (HRs) with 95% CIs in the whole cohort and exposure-discordant twin pairs.

Results

Of 2845 participants, 1464 (51.5%) were female. Incident unemployment was experienced by 944 (33.2%) and incident work disability by 522 (18.3%) participants. Compared with noncases, persistent internalizing problems were associated with unemployment (HR, 1.56; 95% CI, 1.27-1.92) and work disability (HR, 2.32; 95% CI, 1.80-2.99). Similarly, compared with noncases, persistent externalizing problems were associated with unemployment (HR, 1.87; 95% CI, 1.55-2.26) and work disability (HR, 2.38; 95% CI, 1.87-3.03). Persistent cases had overall higher risks of adverse outcomes than episodic cases. After adjustment for familial factors, associations with unemployment were no longer statistically significant, whereas associations with work disability remained or were only slightly reduced.

Conclusions and Relevance

In this cohort study of young Swedish twins, familial factors explained the associations between early-life persistent internalizing and externalizing problems and unemployment; such factors were comparatively less important for the association with work disability. This suggests nonshared environmental factors may be important for the risk of future work disability among young individuals with persistent internalizing and externalizing problems.

Sexual-orientation differences in risk of health-related impaired ability to work and to remain in the paid workforce: a prospective population-based twin study

BACKGROUND

Studies consistently show an increased risk of poor health among sexual minorities (i.e., those identifying as lesbian, gay, bisexual [LGB] or other non-heterosexuals individuals), as compared to those identifying as heterosexual. It is largely unknown whether the increased risk of mental and physical health problems among sexual minorities is also reflected in an increased risk of health-related impaired ability to work, in terms of sickness absence (SA) and disability pension (DP), or successfully remain in the paid workforce. This study made use of a large sample of Swedish twins with self-reported information about sexual behavior in young adulthood to examine sexual orientation difference in SA and DP during a 12-year follow-up period.

METHOD

Data from the Swedish Twin project of Disability pension and Sickness absence (STODS), including Swedish twins born 1959-1985 was used (N = 17,539; n = 1,238 sexual minority). Self-report survey data on sexual behavior was linked to information about SA and DP benefits from the MicroData for Analysis of the Social Insurance database (MiDAS), the National Social Insurance Agency. Sexual orientation differences in SA and DP between 2006 and 2018 was analyzed, as well as, the influence of sociodemographic, social stress exposure (i.e., victimization, discrimination), mental health treatment, and family confounding on these differences.

RESULTS

Compared to heterosexuals, sexual minorities were more likely to having experienced SA and having been granted DP. The odds were highest for DP, where sexual minorities were 58% more likely to having been granted DP compared to heterosexuals. The higher odds for SA due to any diagnosis could largely be explained by sociodemographic factors. The higher odds of SA due to mental diagnosis could partially be explained by increased risk of being exposed to discrimination and victimization, and partially by having received treatment with antidepressant medication. The higher odds of being granted DP could also partially be explain by increased risk of being exposed to social stress and treatment with antidepressant medication.

CONCLUSION

To our knowledge, this is the first study to report on sexual orientation differences in risk of SA and DP in a population-based sample. We found higher period prevalence of both SA and DP among sexual minorities as compared to heterosexuals. The higher odds of SA and DP could partially or fully be explained by sexual orientation differences in sociodemographic factors, exposure to social stress, and antidepressant treatment for depression. Future studies can extend these findings by continuing to investigate risk factors for SA and DP among sexual minorities and how such factors can be reduced.

The predictive role of sickness absence spell durations in associations with inpatient- and specialized outpatient care among a population-based Swedish twin sample

BACKGROUND

The associations between a sickness absence spell duration and patient care have been rarely studied. An assumption is that associations would differ by spell duration and by the patient care type, inpatient- or specialized outpatient, due to severity of diseases and/or conditions. We aimed to investigate sickness absence spells in various spell durations as a predictor for subsequent inpatient- and specialized outpatient care separately, and to study if familial confounding plays a role in these associations.

METHODS

We followed a population-based sample of Swedish twins born 1925-90 with national registers from 2001 for first incident sickness absence spell (days to calculate spell duration categorized into ≤30 days, 31-90 days, 91-180 days and ≥ 181 days), or no sickness absence, and for inpatient- and specialized outpatient care until 2013 (n = 24,975). Cox proportional hazards models were applied for hazard ratios (HR) with 95% confidence intervals (CI) while accounting for covariates and familial confounding.

RESULTS

First incident sickness absence spell across all duration categories was associated with an increased risk of inpatient- (age- and sex adjusted HR 1.28 to 6.05) or specialized outpatient care (HR 1.17-2.50), both in comparison to those without any sickness absence or the shortest sickness absence spell category (1-30 days). The associations remained statistically significant while controlling for covariates or familial confounding.

CONCLUSIONS

First incident sickness absence spell increases the risk of inpatient care or specialized outpatient care regardless of the duration of the sickness absence spell. Hence, incident sickness absence spells should be noted and targeted to actions at workplaces as well as in primary and occupational health care.