Background: Mental stress is associated with higher mortality, but it remains controversial whether the association is causal or a consequence of a higher physical disease burden in those with a high mental stress load. Understanding causality is important when developing targeted interventions. We aimed to estimate the effect of mental stress on mortality by performing a 'natural' experiment using spousal bereavement as a disease-independent mental stressor.
Methods: We followed a population-based matched cohort, including all individuals in Denmark bereaved in 1997-2014, for 17 years. Prospectively recorded register data were obtained for civil and vital status, 39 mental and physical diagnoses, and socioeconomic factors.
Results: In total, 389 316 bereaved individuals were identified and 137 247 died during follow-up. Bereaved individuals had higher all-cause mortality than non-bereaved references in the entire study period. The relative mortality in the bereaved individuals was highest shortly after the loss (adjusted hazard ratio (aHR), first month: 2.50, 95% confidence interval (CI) 2.37-2.63; aHR, 6-12 months: 1.38, 95% CI 1.34-1.42). The excess mortality rate associated with bereavement rose with increasing number of physical diseases (1.33 v. 7.00 excess death per 1000 person-months for individuals with 0 v. ⩾3 physical conditions during the first month) and was exacerbated by the presence of mental illness. The excess mortality among bereaved individuals was primarily due to death from natural causes.
Conclusions: Bereavement was associated with increased short-term and long-term mortality, even after adjustment for morbidities, which suggests that mental stress may play a causal role in excess mortality.
Keywords: Bereavement; comorbidity; epidemiology; mental health; mortality; multimorbidity; psychological; stress; widowhood.