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

•On both the absolute and relative scale, patients with affective disorder had higher risk of somatic diseases.•The risk was especially higher risk of dementia, followed by stroke, hip fracture, and COPD.•For most diseases, but especially migraine, risk estimates seemed slightly lower among patients with bipolar disorder compared to individuals with depression or other affective disorders.•Important exceptions included brain tumors and psoriasis, for which patients with bipolar disorder seemed to have a slightly higher risk.•When comparing the absolute risk estimates to the relative estimates, the absolute risk estimates were higher for more prevalent diseases such as ischemic heart disease, stroke, COPD, hip fracture, migraine, and dementia, while, as expected, slightly lower for the less prevalent diseases such as psoriasis and IBD. Patients 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. A 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. After 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. Limitations include use of register-based data, risk of reverse causation and Berkson's bias. Patients with affective disorder have both higher absolute and relative risk of most somatic diseases except for cancers. Further identifi