Olfactory dysfunction predicts the development of dementia in older patients with type 2 diabetes.

Abstract Aims Olfactory dysfunction is associated with the transition from normal cognition to dementia in persons without type 2 diabetes. This study aimed to investigate whether olfactory dysfunction could be an early marker of future dementia in older patients with type 2 diabetes. Methods This exploratory study included 151 older Japanese outpatients with type 2 diabetes who did not have a diagnosis of probable dementia at baseline. A multivariate logistic regression model was used to determine whether Open Essence (OE) test score at baseline is associated with the development of probable dementia. Results Over 3 years, approximately 9% of the study subjects developed probable dementia. Subjects with olfactory dysfunction at baseline developed probable dementia more frequently than those without. Multivariate logistic regression showed that lower OE test score, higher age, lower Mini-Mental State Examination (MMSE) score, higher total protein concentration, and more frequent use of a sulfonylurea are significantly associated with the development of probable dementia. Stepwise multivariate regression analysis demonstrated that change in OE test score over 3 years is significantly associated with change in MMSE score. Conclusions Our study suggested that olfactory dysfunction precedes the development of probable dementia in older patients with type 2 diabetes.