Prevalence and incidence of mental illness in diabetes: A national population-based cohort study

Background: This study aimed to investigate the prevalence and incidence of mental illness among diabetic patients in Taiwan.Methods: Study subjects were identified by at least one service claim for ambulatory or inpatient care with a principal diagnosis of mental illness, and at least two claims for ambulatory care or one claim for inpatient care with a principal diagnosis of diabetes from 2000 to 2004.Results: The one-year prevalence of mental illness among diabetic patients was 20.6% in 2000, and the cumulative prevalence increased to 42.2% in 2004. Diabetic patients had a higher cumulative prevalence and annual incidence than the general population throughout the observation period. A higher prevalence was associated with age ≥45 and low income, and a lower prevalence with male gender and residing in rural areas. Cox regression analysis revealed that a higher incidence was associated with female gender, age ≥45, and low income.Conclusions: The prevalence and annual incidence density of mental illness in diabetic patients were significantly higher than in the general population. Females had higher prevalence and incidence density of mental illness among diabetic patients. Mental illness in diabetic patients was more prevalent in elderly females of low income, and less in rural areas.