Increasing mortality gap for patients diagnosed with bipolar disorder-A nationwide study with 20 years of follow-up.

Objectives: The primary aim of this study was to examine whether the mortality of patients with bipolar disorder has increased over the past two decades as compared with the background population.

Methods: All patients registered with a bipolar disorder diagnosis in the Danish Psychiatric Research Registry from 1965 until the end of 2014, living in Denmark, alive and below the age of 65 years in the study period from 1995 to 2014 were included. Included patients reaching the age of 65 years during the study period were censored at that time point. Overall standardized mortality ratios (SMRs) were calculated for each calendar year over the study period, and trends in SMR over the study period were examined using linear regression. In addition, the SMRs were stratified according to age groups.

Results: Patients with bipolar disorder had an overall elevated mortality rate relative to the general population with an SMR of 2.8, 95% confidence interval (CI): 2.8-2.9. The highest SMR was found among the youngest (15-29 years: 8.2, 95% CI: 6.7-10.1; 30-34 years: 7.7, 95% CI: 6.4-9.3; 35-39 years: 6.2, 95% CI: 5.4-7.2; 40-44 years: 4.6, 95% CI: 4.1-5.1; 45-49 years: 3.5, 95% CI: 3.3-3.8; 50-54 years: 3.2, 95% CI: 3.0-3.4; 55-59 years: 2.7, 95% CI: 2.6-2.8; and 60-64 years: 2.2, 95% CI: 2.1-2.3). An increase in SMR of 0.03 per year in patients diagnosed with bipolar disorder (P < 0.01) was found.

Conclusions: The mortality gap between patients with bipolar disorder and the general Danish population has widened over the past two decades, which is a cause for concern, although reasons for the increasing mortality gap are unknown.