Hypoglycaemic episodes and risk of dementia in diabetes mellitus: 7-year follow-up study.

OBJECTIVE: We investigated the risk of dementia in patients with type 2 diabetes with or without prior hypoglycaemic episodes.

SUBJECTS AND SETTING: One million subjects randomly selected from the National Health Insurance Research Database, Taiwan.

RESULTS: A total of 15 404 diabetic subjects without prior dementia and a mean age of 64.2 years were enrolled in the study. About 2% (n = 289) of participants had at least one episode of hypoglycaemia in a 3-year period; these subjects were older and more likely to be women and also had higher rates of insulin use and comorbidities compared to those without hypoglycaemia. During a total of 7 years of follow-up (mean and median follow-up, 3.8 and 4.8 years, respectively), 1106 patients with diabetes (7.2%) developed dementia. The incidence rate of dementia was higher in diabetic subjects with [29.9 per 1000 person-years (95% CI 22.1-39.2)] compared to those without [11.1 per 1000 person-years (95% CI 10.3-11.8)] hypoglycaemic episodes. The crude rate ratio (RR) and age- and gender-adjusted RR values for dementia were 2.76 (95% CI 2.06-3.70, P < 0.001) and 1.60 (95% CI 1.19-2.14, P = 0.002), respectively, in diabetic subjects with hypoglycaemia compared to those without hypoglycaemia. Results of Cox proportional hazards analysis revealed that hypoglycaemia, older age, female gender and insulin use were independent predictors of dementia.

CONCLUSION: Adult diabetic patients with prior hypoglycaemia had a significantly increased risk of dementia. The influence of hypoglycaemic episodes on brain function warrants further investigation.