Sleep disturbance and work-related mental strain: A national prospective cohort study of the prediction of subsequent long-term sickness absence, disability pension and mortality.

Aims: Sleep disturbances and work-related mental strain are linked to increased sickness absence and disability pension (DP), but we have no information on synergy effects. The aim of this study was to examine the combined (and separate) association of the two predictors with subsequent long-term work disability and mortality. Methods: A total of 45,498 participants aged 16-64 years were interviewed in the Swedish Surveys of Living Conditions between 1997 and 2013, and were followed up on long-term sickness absence (LTSA; >90 days/year), DP and mortality via national registers until 2016. Crude and multivariable Cox analyses were used to estimate hazard ratios (HR) and 95% confidence intervals (CI). Results: For LTSA, the HRs for sleep disturbances and work-related mental strain were 1.6 (95% CI 1.5-1.7) and 1.3 (95% CI 1.2-1.4), respectively. For DP, the HRs were 2.0 (95% CI 1.8-2.2) and 1.4 (95% CI 1.2-1.5). Mortality was only predicted by sleep disturbances (HR=1.2, 95% CI 1.1-1.4). No synergy effect was seen. Conclusions: Work-related mental strain and, in particular, sleep disturbances were associated with a higher risk of subsequent LTSA and DP, but without synergy effects. Sleep disturbances were also associated with mortality. Exposure to interventions tackling sleep disturbance and prevention of workplace stress may reduce work disability.