Bipolar disorder and medical comorbidities: A Portuguese population-based observational retrospective study (2008–2015)

•Between 2008 and 2015, from a total of 20807 hospitalizations with a primary diagnosis of bipolar disorder (BD), 10.3% had a registered comorbidity.•The most prevalent comorbidity was diabetes (5.9%), followed by chronic pulmonary disease (1.4%), dementia (0.96%), liver disease (0.9%) and cerebrovascular disease (0.8%).•Medical comorbidity had a measurable impact on BD inpatient outcomes, namely on length of stay, in-hospital mortality and discharge destination. This study aimed to use the Charlson Comorbidity Index (CCI) to assess the prevalence of medical comorbidities among hospitalization episodes with a primary Bipolar Disorder (BD) diagnosis, and to analyze its association with hospitalization outcomes. A population-based observational retrospective study was conducted using a Portuguese administrative database containing all mainland public hospitalizations. From 2008–2015, hospitalization episodes with a primary diagnosis of BD were analysed. Outcomes included: length of stay (LoS), in-hospital mortality and discharge destination. Overall, 20807 hospitalization episodes were analysed. Mean±standard deviation age at admission was 47.9±14.3 years, and these episodes mostly refer to women's admissions (66.6%). Median (1st quartile; 3rd quartile) LoS was 16.0 (9.0; 25.0) days. A total of 2145 (10.3%) episodes had ≥1 CCI comorbidities registered, being diabetes the most prevalent. LoS was significantly higher for episodes with secondary diagnoses of congestive heart failure, cerebrovascular disease, dementia, diabetes, renal disease and malignancy (all p