Depressive symptoms and long-term health outcomes: a Danish nationwide register-linked cohort study

Background

Depressive symptoms are common in later life, yet evidence on their long‑term prognostic relevance remains limited. We examine associations between depressive symptoms and subsequent mortality and hospitalisations.

Methods

We conducted a cohort study of 5,623 individuals aged ≥40 years participating in the Danish Survey of Health, Ageing and Retirement in Europe (2004–2015). Survey data were linked to nationwide registries with follow‑up until 2018. Depressive symptoms were defined using the European Depression Scale (EURO‑D), with scores ≥4 indicating depressive symptoms. We estimated relative and absolute mortality risks at age 90 and examined hospitalisation rates adjusted for sociodemographic and health‑related factors.

Results

Overall, 11.5% of men and 22.2% of women reported depressive symptoms. Among 1,017 deaths (18.1%), we found higher mortality among individuals who reported depressive symptoms (relative risk = 1.20; 95% CI 1.08–1.34; absolute risk = 0.15; 95% CI 0.07–0.24). No dose–response association was observed for mortality. Higher mortality was particularly observed among individuals reporting pessimism, loss of appetite, and fatigue. Regarding hospital admissions (n = 16,193), higher hospitalisation rates were observed among individuals with depressive symptoms (incidence rate ratio = 1.54; 95% CI 1.37–1.73), showing a dose–response association. Hospitalisation rates were elevated for cancer and for diseases of the metabolic, nervous, circulatory, respiratory, digestive, and genitourinary systems. Overall, results were consistent across sex.

Conclusions

Depressive symptoms were associated with long‑term differences in survival and healthcare use, indicating that depressive symptomatology may serve as a marker of broad subsequent morbidity. We discuss how these findings may support public health initiatives to improve mental health in midlife.

Key messages

• Depressive symptoms in middle‑ and older age are associated with higher subsequent mortality and hospitalisation rates, independent of sociodemographic and health factors.

• Depressive symptoms are markers of higher subsequent morbidity, with dose–response increases in overall hospitalisation rates and elevated admissions across major disease groups.