However, type 2 diabetes was significantly associated with all-cause dementia (except for Alzheimer’s disease) in APOE ε4 carriers when taking into account the competing risk of Alzheimer’s disease, with a subhazard ratio (sHR) of 1.49, 95% confidence interval (CI) 1.05–2.11, P = 0.025. Here, APOE is linked to type 2 diabetes mellitus.