Impact of type 2 diabetes and its duration on incidence rates of dementia death and medication prescription in the Australian population during 2003-2016

AIMS: To quantify rates of dementia treatment and death among Australians with type 2 diabetes relative to those without diabetes using linked national registries of Australia.

METHODS: The study included 891,418 people with type 2 diabetes registered on the National Diabetes Services Scheme and a randomly sampled, population-based comparison group (n = 1,131,369). Outcomes included dementia death (all-cause dementia, Alzheimer's disease (AD) or vascular dementia), and first prescription of cholinesterase inhibitors or memantine.

RESULTS: Excess dementia risk was observed in the diabetes group for the composite outcome of all-cause dementia death or dementia medication prescription but varied with age at diabetes diagnosis and its duration. At age 70, the rate of dementia death/medication prescription was 1.3 (95 % CI 1.2, 1.3) and 1.1 (95 % CI 1.1, 1.2) times higher in people with ten and five years of diabetes duration, respectively. Individual outcomes showed that diabetes was associated with a higher incidence of vascular dementia death, whereas an increased risk of AD death was only observed beyond ∼ 10 years of diabetes duration. Further, the incidence of dementia medication prescription was lower among people with diabetes.

CONCLUSIONS: A higher incidence of AD death in the setting of 10 + years of diabetes duration coupled with a lower incidence of AD treatment suggests an under-recognition of this dementia phenotype among people with type 2 diabetes.