Does chronotype influence the odds of diabetes comorbidity in bipolar disorder? A cross-sectional analysis of the Our Future Health cohort.

Background Diabetes is common in people with bipolar disorder, particularly men. Both type 2 diabetes and bipolar disorder are associated with evening chronotype, and men of working-age have later chronotypes than women. However, it is not known whether elevated rates of diabetes in bipolar are explained by evening chronotype, nor whether sex differences in chronotype contribute to higher rates of diabetes observed in men with bipolar disorder. Aim To determine whether evening chronotype increases the likelihood of comorbid type 2 diabetes in bipolar disorder, relative to those with no mental health problems. Additionally, to determine whether any effect differs between men and women. Methods Using data from the Our Future Health cohort, we estimated odds ratios for type 2 diabetes by bipolar disorder diagnosis, chronotype, and their interaction, adjusting for relevant covariates. Results A total of 1,136,694 participants (N = 6,846 with bipolar disorder) were included in the adjusted models. Type 2 diabetes was independently associated with bipolar disorder and evening chronotype. There were no significant differences in the interaction effects of chronotype on the odds of type 2 diabetes in bipolar across the whole sample or when stratified by sex. Conclusions The high prevalence of type 2 diabetes in people (and in men, specifically) with bipolar disorder may be independent of evening chronotype.