Study objectives: Depression and insomnia are common and frequently comorbid. Unlike the priority now accorded to depression, insomnia is comparatively ignored as a reason for impaired occupational functioning. The objective of this study was to compare their relative impact upon medically certified disability pension award.
Design: Historical cohort study
Setting: Data from a population-based health survey in Nord-Trøndelag County in Norway (HUNT-2) was linked with a comprehensive national social security database.
Participants: Participants within working age (20-66 years of age) not claiming disability pension (N = 37,302).
Measurements and results: We compared complaints of insomnia and depression as predictors of disability pension award 18-48 months after a health survey. Insomnia complaints and depression each were similarly associated with disability pension award after adjustment for multiple health and sociodemographic factors, with similar odds ratios (1.66 [1.37-2.01] and 1.56 [1.24-1.96] respectively). Comorbidity did not contribute to disability beyond that expected from each condition. Taking the higher prevalence of insomnia complaints into account, insomnia complaints contributed as much or even more than depression to work-related disability.
Conclusions: Depression is regarded as a major contributor to work disability and is increasingly the primary diagnosis in disability pension award. Our results suggest that although rarely reported in official registries of disability pension causes, insomnia has an equally important and independent role, particularly among the younger group. This suggests that this potentially treatable factor has considerable economic impact and should receive more attention in clinical and public health management.