OBJECTIVE: To examine trends in incidence of acute diabetes complications in individuals with type 1 or type 2 diabetes with and without severe mental illness (SMI) in Denmark by age and calendar year.

RESEARCH DESIGN AND METHODS: We conducted a cohort study using nationwide registers from 1996 to 2020 to identify individuals with diabetes, ascertain SMI status (namely, schizophrenia, bipolar disorder, or major depression) and identify the outcomes: hospitalization for hypoglycemia and diabetic ketoacidosis (DKA). We used Poisson regression to estimate incidence rates (IRs) and incidence rate ratios (IRRs) of recurrent hypoglycemia and DKA events by SMI, age, and calendar year, accounting for sex, diabetes duration, education, and country of origin.

RESULTS: Among 433,609 individuals with diabetes, 8% had SMI. Risk of (first and subsequent) hypoglycemia events was higher for individuals with SMI than for those without SMI (for first hypoglycemia event, IRR: type 1 diabetes, 1.77 [95% CI 1.56-2.00]; type 2 diabetes, 1.64 [95% CI 1.55-1.74]). Individuals with schizophrenia were particularly at risk for recurrent hypoglycemia events. The risk of first DKA event was higher in individuals with SMI (for first DKA event, IRR: type 1 diabetes, 1.78 [95% CI 1.50-2.11]; type 2 diabetes, 1.85 [95% CI 1.64-2.09]). Except for DKA in the type 2 diabetes group, IR differences between individuals with and without SMI were highest in younger individuals (<50 years old) but stable across the calendar year.

CONCLUSIONS: SMI is an important risk factor for acute diabetes complication and effective prevention is needed in this population, especially among the younger population and those with schizophrenia.