People with type 1 diabetes have a three-times-greater risk for dementia than those without diabetes; people with type 2 diabetes have double the risk, shows data from the National Institutes of Health’s All of Us Research Program.
“As advances in medical care have extended the lives of people with type 1 diabetes, it’s becoming increasingly important to understand the relation of type 1 diabetes to the risk of dementia,” said study author Jennifer Weuve, MPH, ScD, of Boston University. “We have known that type 2 diabetes is linked to an increased risk of dementia, but this new research suggests that, unfortunately, the association may be even stronger for those with type 1 diabetes.”
Type 1 diabetes is far less prevalent than type 2 diabetes, accounting for around 5% of all diabetes cases, and has historically been associated with a shorter than life expectancy. This has limited research into the late-life health, including dementia risk, of people with type 1 diabetes. Medical records from large studies like All of Us offer researchers an opportunity to better understand the link between the two conditions.
In the current analysis, published in Neurology, the medical journal of the American Academy of Neurology, Weuve and team reviewed data for 283,772 individuals aged 50 years or older (mean age 65 years, 5.7% women). Of these, 5442 (1.9%) had type 1 diabetes and 51,511 (18.2%) had type 2 diabetes.
During an average 2.4Â years of follow-up, 2348 (0.83%) people developed dementia overall. The incidence was 2.6% among people with type 1 diabetes, 1.8% among those with type 2 diabetes, and 0.6% in the participants who did not have diabetes.
After accounting for sociodemographic factors, such as age, sex, race/ethnicity, education level, and household income, the researchers found that the risk for dementia was a significant 2.82-fold higher in people with type 1 diabetes and a significant 2.08-fold higher in those with type 2 diabetes, relative to people without diabetes.
Weuve and team also calculated that an estimated 64.5% of dementia cases among people with type 1 diabetes could be attributed to the diabetes.
“Type 1 diabetes is not common, so this condition accounts for a small fraction of all dementia cases,” noted Weuve. “But for the growing number of people with type 1 diabetes who are over 65 years old, these findings underscore the urgency of understanding the ways in which type 1 diabetes influences dementia risk and how we can prevent or delay it.”
The authors say that their findings provide “strong evidence” that both type 1 and type 2 diabetes are associated with an increased risk dementia, meaning it is important to consider diabetes subtype when evaluating long-term cognitive outcome.
They add that the data “highlight the substantial burden of dementia among individuals with [type 1 diabetes]—particularly relevant because this population continues to age and suggests the need for targeted prevention strategies.”
Weuve and colleagues conclude: “Future research should explore the distinct biological mechanisms linking each diabetes subtype to dementia and quantify the effect of misclassification bias in studies relying on EHR-based diabetes phenotype.”
