An analysis of the relative and absolute incidence of somatic morbidity in patients with affective disorders—A nationwide cohort study

Abstract

BackgroundPatients with affective disorder seem to experience higher risks of several somatic diseases, but no studies have provided estimates of both absolute and relative risks for these diseases in the same population. MethodsA prospective cohort of all patients age ≥18 years old with a hospital contact with affective disorder between 1997-2014 (n=246,282) and a random sample from the background population (n=167,562) was followed for hospitalizations with cardiovascular disease, diabetes, cancers, chronic obstructive pulmonary disease (COPD), asthma, inflammatory bowel disease, hip fracture, psoriasis, migraine, or dementia. Adjusted absolute and relative risk estimates were calculated using multivariable adjusted Aalen's additive and Cox proportional hazard regression models. ResultsAfter adjustments, the absolute risk difference was 130.6 (95% confidence interval [CI] 125.5-135.7) additional cases per 10,000 person-years among affective disorder patients compared to the reference population. The corresponding hazard ratio for any somatic disease was 1.50 (95% CI 1.48-1.52). The strongest associations were found for dementia, hip fracture, COPD, and stroke on both the relative and absolute scale. The patients did not have higher risk of cancers except for lung cancer and brain tumors. Risk estimates tended to be slightly higher for individuals with depression or other affective disorder compared to bipolar disorder. LimitationsLimitations include use of register-based data, risk of reverse causation and Berkson's bias. ConclusionsPatients with affective disorder have both higher absolute and relative risk of most somatic diseases except for cancers. Further identification of the shared mechanisms will facilitate the development of targeted interventions.