Type 2 diabetes is characterized by accelerated cognitive decline and higher dementia risk. Controversy exists regarding the impact of metformin, associated with both increased and decreased dementia rates. This study’s objective was to determine the association of metformin use with incident dementia and cognitive decline over six years in diabetes participants compared with those not receiving metformin and those without diabetes.

This prospective observational study was conducted of N = 1,037 community-dwelling older participants without dementia aged 70–90 years at baseline (the Sydney Memory and Ageing Study). Exclusion criteria were dementia, major neurological or psychiatric disease, or progressive malignancy. Neuropsychological testing measured cognitive function every two years; a battery of tests measured executive function, memory, attention/speed, language, and visuospatial function individually. The result of n = 1,037, 123 had diabetes; 67 received metformin (DM+MF) and were demographically similar to those who did not (DM-noMF) and participants without diabetes (no-DM). DM+MF had significantly slower global cognition and executive function decline compared with DM-noMF. Incident dementia was considerably higher in DM-noMF compared with DM+MF (odds ratio 5.29 [95% CI 1.17–23.88]; P = 0.05).

The study results determined that older people with diabetes receiving metformin have slower cognitive decline and lower dementia risk. Diabetes Care 2020 Nov; 43(11): 2691-2701