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.