A nation-wide population-based longitudinal study mapping physical diseases in patients with bipolar disorder and their siblings

Background: Patients with bipolar disorder may have increased risk of physical diseases due to genetic and environmental factors, but no study has systematically mapped all physical comorbidities in such subjects. The aim was to map rates of all physical diseases among patients and siblings to patients with bipolar disorder. Methods: We used Danish nation-wide population-based longitudinal register linkage to identify 19.955 patients with bipolar disorder, their 13.923 siblings and 20 sex, age and calendar matched control individuals from the general population. Follow-up was from 1995 to 2017. Results: Bipolar disorder was associated with increased rates of all physical disease categories compared with rates for control individuals, except for cancer. Further, bipolar disorder was associated with increased rates of separate disorders including ischemic heart disease, diabetes, dementia, hypertension, hypercholesterolemia and hyperlipidemia, hypothyroidism and infections. In contrast, siblings to patients with bipolar disorder who were unaffected by bipolar disorder had increased rates of certain disorders, only, comprising infectious and parasitic diseases, and diseases of the nervous system, digestive system and genitourinary system. Limitations: Underdetection of physical disorders is likely because data are not available for persons who do not seek help for their disorders. Conclusions: Bipolar disorder was associated with increased rates of all physical diseases categories, except cancer, and with separate disorders, likely involving inflammatory components in the pathogenesis. In contrast, unaffected siblings to patients with bipolar disorder had increased rates of certain disorders, only.