Digital self-management of hip and knee osteoarthritis and trajectories of work and activity impairments

OBJECTIVE

To investigate the trajectories of work and activity impairments among people participating in a digital self-management program for osteoarthritis (OA).

METHODS

We conducted an observational longitudinal study using data for baseline, 3, 6, 9 and 12 months follow ups from people participating in a digital OA treatment between June 2018 and September 2021. The Work Productivity and Activity Impairment-Osteoarthritis (WPAI-OA) questionnaire was used to measure work and activity impairments. We applied linear mixed models and group-based trajectory modelling (GBTM) to assess the trajectories of work and activity impairments and their variability. Dominance analysis was performed to explore the relative importance of baseline characteristics in predicting the trajectory subgroup membership.

RESULTS

A total of 14,676 participants with mean (± standard deviation) age 64.0 (± 9.1) years and 75.5% females were included. The adjusted mean improvements in work impairment from baseline were 5.8% (95% CI 5.3, 6.4) to 6.1% (95% CI 5.5, 6.8). The corresponding figures for activity impairment were 9.4% (95% CI 9.0, 9.7) to 11.3% (95% CI 10.8, 11.8). GBTM identified five (low baseline-declining, moderate baseline-declining, high baseline-declining, very high baseline-substantially declining, and very high baseline-persistent) and three (low baseline-declining, mild baseline-declining, high baseline-declining) subgroups with distinct trajectories of activity and work impairments. Dominance analysis showed that baseline pain was the most important predictor of membership in trajectory subgroups.

CONCLUSION

While participation in a digital self-management program for OA was, on average, associated with improvements in work and activity impairments, there were substantial variations among the participants. Baseline pain may provide useful insights to predict trajectories of work and activity impairments.

Are there non-linear relationships between alcohol consumption and long-term health?: a systematic review of observational studies employing approaches to improve causal inference

Background

Research has long found ‘J-shaped’ relationships between alcohol consumption and certain health outcomes, indicating a protective effect of moderate consumption. However, methodological limitations in most studies hinder causal inference. This review aimed to identify all observational studies employing improved approaches to mitigate confounding in characterizing alcohol–long-term health relationships, and to qualitatively synthesize their findings.

Methods

Eligible studies met the above description, were longitudinal (with pre-defined exceptions), discretized alcohol consumption, and were conducted with human populations. MEDLINE, PsycINFO, Embase and SCOPUS were searched in May 2020, yielding 16 published manuscripts reporting on cancer, diabetes, dementia, mental health, cardiovascular health, mortality, HIV seroconversion, and musculoskeletal health. Risk of bias of cohort studies was evaluated using the Newcastle-Ottawa Scale, and a recently developed tool was used for Mendelian Randomization studies.

Results

A variety of functional forms were found, including reverse J/J-shaped relationships for prostate cancer and related mortality, dementia risk, mental health, and certain lipids. However, most outcomes were only evaluated by a single study, and few studies provided information on the role of alcohol consumption pattern.

Conclusions

More research employing enhanced causal inference methods is urgently required to accurately characterize alcohol–long-term health relationships. Those studies that have been conducted find a variety of linear and non-linear functional forms, with results tending to be discrepant even within specific health outcomes.

Trial registration

PROSPERO registration number CRD42020185861.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12874-021-01486-5.

The role of familial confounding in the associations of physical activity, smoking and alcohol consumption with early exit from the labour market

We investigated the associations between health behaviors and sustainable working life outcomes including all-cause disability pension, disability pensions due to musculoskeletal and mental diagnoses and unemployment. The role of familial factors behind these associations was studied by analysing discordant twin pairs. Our data included Swedish twins born in 1925-1986 (51891 twin individuals). Baseline data based on two independent surveys in 1998-2003 and 2005-2006 for health behaviors were linked to national registers on disability pension and unemployment until 2016. Cox proportional hazards models for hazard ratios (HR) with 95% confidence intervals (CI) were estimated for the whole sample adjusting for covariates. Analyses of health behavior discordant twin pairs (n = 5903 pairs) were conducted using conditional Cox models. In the whole cohort, the combination of healthy behaviors was associated with lower risk for all-cause disability pension, disability pension due to musculoskeletal diagnoses or mental diagnoses, and for unemployment (HRs 0.56-0.86, 95% CIs 0.51-0.92) as did being physically active (HRs 0.69-0.87, 95% CI 0.65-0.92). The discordant pair analyses confirmed the lower risk among those having healthy behaviors (HR 0.70-0.86) or being physically active (HR 0.86-0.87) for all-cause disability pension, disability pension due to musculoskeletal diagnoses, and for unemployment. To conclude, controlling the effects of covariates or familial confounding (i.e. discordant twin pair analyses) shows that being physically active or having several healthy behaviors predict better working life outcomes. This points towards independent association between healthy behavior and longer working life.

Self-reported sickness absence and presenteeism as predictors of future disability pension: Cohort study with 11-year register follow-up

Many healthcare workers in eldercare are pushed out of the labor market before the official retirement age due to poor health. Identification of early warnings signs is important to avoid complete loss of work ability. The aim of this study was to investigate to what degree sickness absence and presenteeism increase future risk for disability pension among eldercare workers. A total of 8952 Danish female eldercare workers responded to a survey about work environment and health. They were followed for 11 years in the Danish Register for Evaluation of Marginalization, with time-to-event analyses estimating the hazard ratios (HRs) for disability pension from sickness absence and presenteeism at baseline. Analyses were adjusted for age, education, body mass index, leisure-time physical activity, smoking, physical exertion at work, and psychosocial factors related to the work environment. During the 11-year follow-up, 11.9% participants received disability pension. For the whole cohort, the highest risk for disability pension was observed for the category of >30 days of combined sickness absence and presenteeism at baseline in the fully adjusted model (HR = 7.93 [95%CI 5.20-12.09]). Eldercare workers aged >45 years were at a higher risk for disability pension in all included categories. Sickness absence and presenteeism increased the risk of disability pension among female eldercare workers. These results suggest that organizations would benefit from identifying early warning signs among workers in the prevention of involuntary early retirement.

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.

Health behaviours and psychosocial working conditions as predictors of disability pension due to different diagnoses: a population-based study

BACKGROUND

To investigate whether the clustering of different health behaviours (i.e. physical activity, tobacco use and alcohol consumption) influences the associations between psychosocial working conditions and disability pension due to different diagnoses.

METHODS

A population-based sample of 24,987 Swedish twins born before 1958 were followed from national registers for disability pension until 2013. Baseline survey data in 1998-2003 were used to assess health behaviours and psychosocial Job Exposure Matrix for job control, job demands and social support. Cox proportional hazards models were used to calculate hazard ratios (HR) with 95% confidence intervals (CI).

RESULTS

During follow-up, 1252 disability pensions due to musculoskeletal disorders (5%), 601 due to mental diagnoses (2%) and 1162 due to other diagnoses (5%) occurred. In the models controlling for covariates, each one-unit increase in job demands was associated with higher (HR 1.16, 95%CI 1.01-1.33) and in job control with lower (HR 0.87, 95%CI 0.80-0.94) risk of disability pension due to musculoskeletal disorders among those with unhealthy behaviours. Among those with healthy behaviours, one-unit increase of social support was associated with a higher risk of disability pension due to mental and due to other diagnoses (HRs 1.29-1.30, 95%CI 1.04-1.63).

CONCLUSIONS

Job control and job demands were associated with the risk of disability pension due to musculoskeletal disorders only among those with unhealthy behaviours. Social support was a risk factor for disability pension due to mental or other diagnoses among those with healthy behaviours. Workplaces and occupational health care should acknowledge these simultaneous circumstances in order to prevent disability pension.

Evaluation of a multimodal pain rehabilitation programme in primary care based on clinical register data: a feasibility study

Aim:

Investigate the feasibility of identifying a well-defined treatment group and a comparable reference group in clinical register data.

Background:

There is insufficient knowledge on how to avert neck/back pain from turning chronic or to impair work ability. The Swedish Government implemented a national multimodal rehabilitation (MMR) programme in primary care intending to promote work ability, reduce sick leave and increase return to work. Since randomised control trial data for effect is lacking, it is important to evaluate existing observational data from clinical settings.

Methods:

We identified all unique patients with musculoskeletal pain (MSP) diagnoses undergoing the MMR programme in primary care in the Skåne Health care Register (n = 2140) during 2010–2011. A reference cohort in primary care (n = 56 300) with similar MSP diagnoses, same ages and the same level of sick leave before baseline was identified for the same period. The reference cohort received ordinary care and treatment in primary care. The final study group consisted of 603 eligible MMR patients and 2874 eligible reference patients. Socio-economic and health-related baseline data including sick leave one year before up to two years after baseline were compared between groups.

Findings:

There were significant socio-economic and health differences at baseline between the MMR and the reference patients, with the MMR group having lower income, higher morbidity and more sick leave days. Sick leave days per year decreased significantly in the MMR group (118–102 days, P < 0.001) and in the reference group (50–42 days, P < 0.001) from one year before baseline to two years after.

Conclusions:

It was not feasible to identify a comparable reference group based on clinical register data. Despite an ambitious attempt to limit selection bias, significant baseline differences in socio-economic and health were present. In absence of randomised trials, effects of MMR cannot be sufficiently evaluated in primary care.

Life events as predictors for disability pension due to musculoskeletal diagnoses: a cohort study of Finnish twins

Purpose

Musculoskeletal diagnoses (MSD) are one of the largest diagnostic groups for disability pensions (DP). This study investigated the associations between life events and DP due to MSD, considering sociodemographic, health, and familial factors.

Methods

The study sample included 18,530 Finnish twins, 24–64 years old at baseline, who responded to a questionnaire in 1981 including a 21-item life event inventory. Information on DP with diagnosis codes (ICD codes: M00–M99) were obtained from the official national pension registers. Life events were divided into family- and work-related events. “Positive change in life” was analyzed separately. Cox proportional hazards models were used to calculate hazard ratios (HR) with 95% confidence intervals (CI).

Results

During the follow-up of 23 years, 1273 (7%) individuals were granted DP due to MSD. In discordant pair analysis, family-related events (≥ 4 events) increased (HR 1.63, 95% CI 1.31, 2.03) and the absence of such events decreased (HR 0.68, 95% CI 0.48, 0.95) the risk of DP due to MSD. For work-related events (≥ 3 events), the risk estimates were non-significant when controlling for familial factors. Having had a positive change in life decreased the risk of DP due to MSD (HR 0.79, 95% CI 0.65, 0.96) while controlling for familial confounding, but were non-significant in the full model controlling for various covariates (HR 0.91, 95% CI 0.75, 1.12).

Conclusions

The associations between life events and the risk of DP due to MSD are complex and potentially affected by familial and other confounding factors including sociodemographics and health.

Body mass index and the risk of disability retirement: a systematic review and meta-analysis

The aim of this study was to determine the associations of body mass index (BMI) with all-cause and cause-specific disability retirement. Literature searches were conducted in PubMed, Embase and Web of Science from their inception to May 2019. A total of 27 (25 prospective cohort and 2 nested case-control) studies consisting of 2 199 632 individuals qualified for a meta-analysis. Two reviewers independently assessed the methodological quality of the included studies. We used a random effects meta-analysis, assessed heterogeneity and publication bias, and performed sensitivity analyses. There were a large number of participants and the majority of studies were rated at low or moderate risk of bias. There was a J-shaped relationship between BMI and disability retirement. Underweight (hazard ratio (HR)/risk ratio (RR)=1.20, 95% CI 1.02 to 1.41), overweight (HR/RR=1.13, 95% CI 1.07 to 1.19) and obese individuals (HR/RR=1.52, 95% CI 1.36 to 1.71) were more commonly granted all-cause disability retirement than normal-weight individuals. Moreover, overweight increased the risk of disability retirement due to musculoskeletal disorders (HR/RR=1.26, 95% CI 1.15 to 1.39) and cardiovascular diseases (HR=1.73, 95% CI 1.24 to 2.41), and obesity increased the risk of disability retirement due to musculoskeletal disorders (HR/RR=1.66, 95% CI 1.42 to 1.94), mental disorders (HR=1.29, 95% CI 1.04 to 1.61) and cardiovascular diseases (HR=2.80, 95% CI 1.85 to 4.24). The association between excess body mass and all-cause disability retirement did not differ between men and women and was independent of selection bias, performance bias, confounding and adjustment for publication bias. Obesity markedly increases the risk of disability retirement due to musculoskeletal disorders, cardiovascular diseases and mental disorders. Since the prevalence of obesity is increasing globally, disease burden associated with excess body mass and disability retirement consequently are projected to increase. Reviewregistrationnumber: CRD42018103110.

Trajectories of future sickness absence and disability pension days among individuals with a new sickness absence spell due to osteoarthritis diagnosis ≥21 days: a prospective cohort study with 13-month follow-up

INTRODUCTION

Osteoarthritis is one of the most common types of musculoskeletal diagnoses also among working-age populations, and often leads to long-term sickness absence (SA) spells or even disability pension (DP).

THE AIM

was to identify future trajectories of days of SA and/or DP among people with a new SA spell due to osteoarthritis that became ≥21 long, and to investigate sociodemographic and morbidity characteristics of individuals in identified trajectories.

METHODS

This is a prospective population-based cohort study using data from several Swedish registers. We studied future SA/DP among all 4894 individuals aged 16-64 years who, during the first 6 months of 2010, had an incident SA spell due to osteoarthritis (ICD-10 codes M15-19) ≥21 days. Using group-based trajectory modelling, we identified trajectories of mean SA/DP net days/month and 95% CIs for the 13 months from the 21st day of the index SA spell. Sociodemographic and morbidity characteristics were compared by χ² tests and multinomial logistic regression.

RESULTS

We identified five trajectories of SA/DP days: 'fast decrease' (36% of the cohort), 'medium fast decrease' (29%), 'slow decrease' (15%), 'fluctuating' (12%) and 'late decrease' (8%). Individuals in the two trajectories who still had SA/DP days at end of follow-up (late decrease and fluctuating) were more likely to be older, born outside the EU and have indicators of more severe morbidity than those in the other trajectories.

CONCLUSION

Five trajectories of future SA/DP days were identified; 80% of the cohort belonged to trajectories with no SA/DP by the end of follow-up. Identifying trajectories of future SA/DP provides new insights regarding the developments of SA/DP over time among people on SA due to osteoarthritis; not only days in the initial SA spell but also in new spells during follow-up need to be included for a better understanding.

Night work as a risk factor for future cause-specific disability pension: A prospective twin cohort study in Sweden

The objectives of the study were to investigate the associations between night work and disability pension (DP) due to all causes, cardiovascular (CVD), mental, and other diagnoses, adjusting for familial confounding. The material of the study included comprehensive survey data on 27 165 Swedish twins born in 1935-1958 that were linked with DP data for the survey period (1998-2003) to 2013. Night work was assessed as years of working nights at least every now and then, and categorized into not at all, 1-10 years and over 10 years. For statistical analyses, Cox proportional hazards regressions were used to calculate hazard ratios (HRs) with 95% confidence intervals (CIs). The results of the study indicated that over 10 years duration of night work had an age- and sex-adjusted HR of 1.48 (95% CI 1.11-1.98) for DP due to CVD and 1-10 years of night work an HR of 1.28 (95% CI 1.06-1.55) for DP due to mental diagnoses, but attenuated when covariates were adjusted for. Both 1-10 years (HR 1.27, 95% CI 1.17-1.39) and >10 years of night work (HR 1.20, 95% CI 1.08-1.34) were associated with DP due to all causes and other diagnoses. These risks remained after adjusting for covariates. To conclude, even modest exposure in terms of duration of night work is a risk factor for all-cause DP, but also for DP due to mental and other diagnoses. The risk of DP due to CVD seems to be associated with longer (>10 years) periods of night work. All the associations between night work and DP seem to be influenced by various covariates.

Changes in leisure time physical activity and subsequent disability retirement: A register-linked cohort study

Background

Disability retirement is an economic, public health and work life issue causing costs for employees, workplaces and society. Adopting physical activity at middle-age has been associated with reduced risk of sickness absence and mortality. The aim of this study was to examine how changes over time in leisure time physical activity are associated with subsequent disability retirement among midlife employees.

Methods

The Helsinki Health Study cohort baseline (phase 1) mail questionnaire survey data were collected in 2000, 2001 and 2002 among 40–60-year-old employees of the City of Helsinki, Finland. A phase 2 survey was conducted in 2007 (N = 3943). Respondents were classified into three groups: 1. low-active (<14 MET-hours/week), 2. moderately active (> = 14 MET-hours/week in moderate-intensity physical activity) and 3. vigorously active (> = 14 MET-hours/week including vigorous physical activity) at both phases. This yielded nine groups for describing stability and change of leisure time physical activity. Disability retirement data were derived from the registry of the Finnish Centre for Pensions until the end of 2013. A Cox regression analysis was used to calculate hazard ratios (HR) and their 95 % confidence intervals (CI) adjusting for covariates.

Results

During the follow-up, 264 (6.7 %) participants retired due to disability. Compared with those who were persistently low-active, those who increased their physical activity from low to vigorous had a lower risk of subsequent disability retirement (HR = 0.38, 95 % CI = 0.15–0.97) when adjusting for age, gender, occupational social class, strenuousness of work, smoking and binge drinking. Similarly, compared with those who were persistently moderately active, those increasing from moderate to vigorous (HR = 0.50, 95 % CI = 0.28–0.86) had a reduced risk. In contrast, those decreasing their physical activity from vigorous to low (HR = 2.42, 95 % CI = 1.32–4.41) or moderate (HR = 1.70, 95 % CI = 1.03–2.82) had an increased risk, compared with those who were persistently vigorously active. Adjusting for BMI, limiting longstanding illness and prior sickness absence somewhat attenuated the associations.

Conclusions

Adopting vigorous physical activity was associated with a reduced risk of disability retirement. Promoting vigorous physical activity among midlife employees may help prevent disability retirement.

Stability and change of body mass index as a predictor of disability pension

AIMS

To investigate whether stability or change in body mass index (BMI) predict disability pension (DP) due to musculoskeletal diagnosis (MSD) when controlling for familial confounding.

METHODS

Our study cohort consisted of 17,169 Finnish twins born before 1958. Data on BMI and multiple covariates from questionnaires in 1975 and 1981 were included and DPs were collected from the national pension registers until the end of 2004. Cox proportional hazards regression models with Hazard Ratios (HR) and 95% Confidence Intervals (CI) were used for statistical analyses.

RESULTS

General DP was granted to 2853 individuals and DP due to MSD to 1143 individuals during the 23-year follow-up. A one-unit increase in BMI in both 1975 (HR 1.08, 95% CI 1.05, 1.10) and 1981 (HR 1.06, 95% CI 1.04, 1.07), as well as the stability of and change in BMI from 1975 to 1981 were all associated with an increased risk of DP. These associations held in the analyses controlling for multiple covariates (age, sex, socioeconomic status, education, marital status, leisure-time physical activity, and musculoskeletal pain), and mainly also familial confounding, that is, genetics and shared environment. HR for stable obesity was 2.28 (95% CI 1.69, 3.08) for DP due to MSD, and 1.91 (95% CI 1.56, 2.34) for general DP in the fully adjusted models. CONCLUSIONS BMI IS AN EARLY PREDICTOR OF GENERAL DP AND ALSO OF DP DUE TO MSD OWING TO THE INDEPENDENCY OF VARIOUS COVARIATES AND POTENTIALLY ALSO FAMILIAL CONFOUNDING, BMI MAY POSSIBLY HAVE A DIRECT EFFECT ON THE RISK OF DP.

Socioeconomic inequities in perceived health among patients with musculoskeletal disorders compared with other chronic disorders: results from a cross-sectional Dutch study

OBJECTIVES

To explore the impact of socioeconomic factors on physical and mental health of patients with musculoskeletal disorders (MSKDs) and compare it across patients with other disorders.

METHODS

A representative sample of the Dutch population (n=8904) completed a survey on sociodemographics, physician-diagnosed (co-) morbidities, and physical (physical component summary, PCS) and mental (mental component summary, MCS) subscales of SF-12 (outcome variables). Regression models were computed first in the total group of patients with MSKDs, with education, age, gender, origin and place of residence as independent variables, and, second, in individuals expected to have paid work, adding a variable on social status. Models were repeated for five other subgroups of chronic disorders (cardiovascular (CVD), diabetes, cancer, mental and respiratory) and for healthy individuals.

RESULTS

MSKDs confirmed by a physician were reported by 1766 (20%) participants (mean age 59 years, 38% male), 547 (6%) respondents reported to have diabetes, 1855 (21%) CVD, 270 (3%) cancer, 526 (6%) mental disorders, 679 (8%) respiratory disorders and 4525 (51%) did not report any disease. In patients with MSKDs, (primary school vs university education (-5.3 (PCS) and -3.3 (MCS)) and having a state subsidy vs paid work (-5.3 (PCS) and -4.7 (MCS)) were consistently associated with worse physical and mental health. Gender was only relevant for PCS (female vs male -2.1). Comparable differences in health by education and social status were observed in the other diseases, except for cancer.

CONCLUSIONS

Education and social status in MSKD have the same strong and independent association with health as in other chronic diseases. These health gradients are unfair and partly avoidable, and require consorted attention and action in and outside healthcare.

Prevalence of all-cause and diagnosis-specific disability pension at the time of first coronary revascularisation: a population-based Swedish cross-sectional study

BACKGROUND

Although coronary revascularisation by coronary artery bypass graft surgery (CABG) and percutaneous coronary intervention (PCI) is well documented, scientific knowledge on disability pension (DP) at the time of revascularisation is lacking. The aim was to investigate the prevalence of all-cause and diagnosis-specific DP at the time of a first coronary revascularisation, accounting for socio-demographic and medical factors.

MATERIALS AND METHODS

A population-based cross-sectional study using Swedish registers was conducted including all 65,676 patients (80% men) who when aged 30-63 years, within 1994-2006, had a first CABG (n = 22,959) or PCI (n = 42,717) and did not have old-age pension. Associations between socio-demographic and medical factors and the probability of DP were estimated by odds ratios (OR) with 95% confidence intervals (CI) using logistic regression analyses.

FINDINGS

The prevalence of DP at time of revascularisation was 24%, mainly due to musculoskeletal diagnoses. Sixty-two percent had had DP for at least four years before the revascularisation. In the multivariable analyses, DP was more common in women (OR: 2.40; 95% CI: 2.29-2.50), older patients (50-63 years); especially men aged 60-63 years with CABG (OR: 4.91; 95% CI: 4.27-5.66), lower educational level; especially men with PCI (OR: 2.96; 95% CI: 2.69-3.26), patients born outside Sweden; especially men with PCI (OR: 2.11; 95% CI: 1.96-2.27), and in women with an indication of other diagnoses than acute coronary syndrome (ACS) or stable angina pectoris for PCI (OR: 1.72; 95% CI: 1.31-2.24).

CONCLUSION

About a quarter had DP at the time of revascularisation, often due to musculoskeletal diagnoses. More than half had had DP for at least four years before the intervention. DP was associated with female gender, older age, lower educational level, and being born outside Sweden.

Leisure-time physical activity and disability pension: 9 years follow-up of the HUNT Study, Norway

The objective of this study was to prospectively examine the association between leisure-time physical activity and risk of disability pension, as well as risk of disability pension because of musculoskeletal or mental disorders in a large population-based cohort. Data on participants aged 20-65 years in the Norwegian Nord-Trøndelag Health Study 1995-1997 (HUNT2) were linked to the National Insurance Database. Cox regression was used to calculate hazard ratios (HR) and 95% confidence intervals for disability pension across physical activity categories. During a follow-up of 9.3 years and 235,657 person-years, 1266 of 13,823 men (9%) and 1734 of 14,531 women (12%) received disability pension. Compared with individuals in the inactive group, those in the highly active group had a 50% lower risk of receiving disability pension (HR for men: 0.50, 0.40-0.64; women: 0.50, 0.39-0.63). After comprehensive adjustment for potential confounders, the risk remained 32-35% lower (HR for men: 0.68, 0.53-0.86; women: 0.65, 0.51-0.83). The associations were stronger for disability pension due to musculoskeletal disorders than mental disorders. In summary, we observed strong inverse associations between leisure-time physical activity and disability pension. Our findings strengthen the hypothesis that leisure-time physical activity may be important for occupational health in reducing disability pension.

Part-time work or social benefits as predictors for disability pension: a prospective study of Swedish twins

BACKGROUND

To a large extent, it is unknown whether work absences other than sickness absence (SA) covered by social benefits such as parental leave, rehabilitation, or unemployment would predict disability pension (DP).

PURPOSE

We investigated whether part-time work or having received social benefits for sick leave, rehabilitation, or parental leave would be predictors for DP taking into account familial confounding (genetics and shared environment, e.g., social background) in these associations.

METHOD

A sample of 17,640 same-sex Swedish twin ndividuals [corrected] was followed from 2000 to 2008 via national registries for their receipt of social benefits and DP including additional baseline questionnaire data. Cox proportional hazard ratios were estimated.

RESULTS

Full-time work was less common (47 %) among those being granted DP during the follow-up compared to those without DP (69 %). Self-reported full-time work, part-time work (≥50 %), and self-employment and registry data of caring for a child were the direct protective factors, whereas self-reported part-time work (<50 %) and long-term SA and registry data on SA, compensation for rehabilitation, and benefits during return to work were the direct risk factors for DP, i.e., independent of familial confounding.

CONCLUSION

Part-time work and social benefits play different roles in predicting DP. Thus, full-time work, part-time work (≥50 %), self-employment, and benefits for parental leave seem to protect from DP. In contrast, SA and part-time work (<50 %) carry a highly increased risk for DP. Although these associations were mainly independent from several mediating factors, some of the associations seem to be influenced by family situation, social benefits, or severity of diseases.

Persistent smoking as a predictor of disability pension due to musculoskeletal diagnoses: a 23 year prospective study of Finnish twins

OBJECTIVE

To investigate whether stability or changes in smoking predict disability pension (DP) due to low back diagnoses (LBD) and musculoskeletal diagnoses (MSD) after taking familial confounding into account using a co-twin design.

METHOD

Longitudinal smoking patterns and multiple covariates in a population-based cohort of 17,451 Finnish twins (6959 complete pairs) born before 1958 were surveyed through questionnaires in 1975 and 1981. The outcome data were collected from the national pension registers until the end of 2004. Cox proportional hazards regression models were used for statistical analyses.

RESULTS

Disability pension due to low back diagnoses was granted to 408 individuals and disability pension due to musculoskeletal diagnoses to 1177 individuals during the follow-up of 23 years. Being a persistent smoker (current smoker both 1975 and 1981) predicted a significantly increased risk for disability pension (hazard ratio 1.69, 95% confidence interval 1.46, 1.97) compared to those individuals who had never smoked. The association remained when several confounding factors, including familial factors, were taken into account.

CONCLUSION

Persistent smoking predicts early disability pension due to musculoskeletal diagnoses and low back diagnoses independently from numerous confounding factors, including familial effects shared by the co-twins.

Noise sensitivity and disability retirement: a longitudinal twin study

OBJECTIVE

To analyze whether noise sensitivity increases the risk of disability pension (DP).

METHODS

Questionnaire data of a sample of 706 Finnish twin individuals (age range, 31 to 65 years) with record linkage to information on DP during 16 years of follow-up were analyzed using individual and pairwise Cox proportional hazards models.

RESULTS

Noise sensitivity increased the risk of DP (hazard ratio = 1.41; 95% confidence interval [CI]: 1.03 to 1.93) and DP due to musculoskeletal disorders (hazard ratio = 1.63; 95% CI: 1.00 to 2.66). In within-pair analyses, noise sensitivity increased the risk of DP: among all twin pairs, odds ratio was 1.80 (95% CI: 1.08 to 3.06).

CONCLUSIONS

Noise sensitivity may be a potential risk factor for disability retirement. It is associated with DP independently of familial background and genetic factors.

A prospective cohort study of disability pension due to mental diagnoses: the importance of health factors and behaviors

BACKGROUND

Previous studies have found associations between various health factors and behaviors and mental disorders. However, knowledge of such associations with disability pension (DP) due to mental diagnoses is scarce. Moreover, the influence of familial factors (genetics and family background) on the associations are mainly unknown. The aim of the study was to investigate associations between health factors and behaviors and future DP due to mental diagnoses in a twin cohort, accounting for familial confounding.

METHODS

A prospective cohort study of Swedish twins (N=28 613), including survey data and national register data on DP and other background factors was conducted. Cox proportional hazards regression models were used to calculate hazard ratios (HR) with 95% confidence intervals (CI) for the whole twin cohort, and for discordant twin pairs.

RESULTS

During follow-up 1998-2008 (median 10 years), 2.2% of the cohort was granted a DP with a mental diagnosis. In the fully adjusted analyses of the whole cohort, the associations of poor or moderate self-rated health (SRH), under- or overweight, former or current tobacco use, or being an abstainer from alcohol were significantly associated with risk of DP due to mental diagnoses. Analyses of discordant twin pairs confirmed all these associations, except for current tobacco use, being independent from familial confounding. Exclusion of individuals with current or previous depression or anxiety at baseline did not influence the associations found.

CONCLUSIONS

Poor or moderate SRH, under- or overweight, former tobacco use or being an abstainer from alcohol seem to be strong direct predictors of DP due to mental diagnoses, independently of several confounders of this study, including familial factors.

Genetic susceptibility to sickness absence is similar among women and men: findings from a Swedish twin cohort

Previous studies of risk factors for sickness absence (SA) focus primarily on psychosocial and work environmental exposures. The aim of this study was to investigate the relative contribution of genetic influences on SA among women and men. The population-based study sample of Swedish twins (34,547) included 13,743 twin pairs of known zygosity, 3,495 monozygotic, 5,073 same-sexed dizygotic, and 5,175 opposite sexed. The point prevalence of long-term SA (≥15 days) in each zygosity and sex group was calculated. The risk of SA was estimated as an odds ratio (OR) with 95% confidence intervals (CI) where the odds for twins on SA to have a co-twin on SA was compared to the OR for SA in twins whose co-twin were not sickness absent. Intrapair correlations and probandwise concordance rates were calculated and standard biometrical genetic model-fitting methods were used to estimate the heritability of SA. The prevalence of SA was 8.8% (women 10.7%; men 6.5%). Intrapair similarity was higher among monozygotic than dizygotic twin pairs. The best-fitting model showed no sex differences in genetic effects or variance components contributing to SA. The heritability estimate was 36% (95% CI: 35-40%). Results suggest genetic contribution to the variation of SA and that environmental factors have an important role, for women and men. As SA seem to be influenced by genetic factors, future studies of associations between risk factors and SA should consider this potentially confounding effect.

Incidence of disability pension and associations with socio-demographic factors in a Swedish twin cohort

PURPOSE

The incidence of disability pension (DP), especially due to mental diagnoses, has increased in many countries, but knowledge of socio-demographic risk factors for DP is limited. Further, the influences of genetics and early-life factors (jointly called familial factors) on these associations remain to be studied. The aims were to study incidence of DP (due to all and mental diagnoses) and associations with socio-demographic factors, and also to establish whether associations differ with DP diagnosis and sex, and are influenced by familial factors.

METHODS

A prospective cohort study of all twins born in 1928-1958 (n = 52,609) in Sweden was conducted. The twins were followed from 1993 to 2008 regarding DP. Cox proportional hazard models were applied.

RESULTS

The cumulative incidence of DP was 17 %. Of all the DP diagnoses 20 % were mental. Higher age (≥45 years), being a woman or unmarried, and/or living in a semi-urban area were risk factors for DP. Low education, being a blue-collar worker or being self-employed predicted either higher (all diagnoses) or lower (mental diagnoses) risk of DP. Rural areas were associated with DP due to mental diagnoses. The estimates varied for men and women. After adjustment for familial factors the associations of DP with education and marital status were attenuated and no longer significant. Similar results were apparent for DP due to mental diagnoses and socioeconomic status.

CONCLUSIONS

Familial factors may select individuals into some of the established risk environments for DP. Studies investigating the causes of DP need to take such confounding into account.

Personality traits and life dissatisfaction as risk factors for disability pension due to low back diagnoses: a 30-year longitudinal cohort study of Finnish twins

OBJECTIVE

Little is known about the association of mild symptoms and mental well-being with risk of disability pension (DP) due to somatic diagnoses, even less for DP due to low back diagnoses (LBD). Moderate genetic influences on personality traits, life dissatisfaction and DP exist suggesting that shared genetic influences may underlie these associations. One can control for familial confounding (genetics and family environment) by examining twins. This twin study aimed to investigate personality traits and life dissatisfaction as predictors for DP due to LBD accounting for familial confounding.

METHODS

Data on 24043 twins aged 18-65year in a baseline survey in 1975 was followed up from national DP register data until 2004. Personality traits were assessed using the short version of the Eysenck Personality Inventory and life dissatisfaction was measured with a four item scale on levels of interest, happiness, easiness, and loneliness of life. Cox proportional hazards regression was used to calculate hazard ratios (HR) with 95% confidence intervals (CI).

RESULTS

DP due to LBD was granted to 537 individuals during the follow-up. Each one unit increase in life dissatisfaction (HR 1.06; 95%CI 1.03, 1.10) and neuroticism (1.07; 1.03, 1.10) but not extroversion was significantly associated with an elevated risk for DP due to LBD. These associations with life dissatisfaction and neuroticism remained when socioeconomic status, education, and marital status were taken into account, and demonstrated an independence from familial confounding.

CONCLUSION

Life dissatisfaction and neuroticism seems to be early, perhaps causal risk factors for DP due to LBD.