Type 1 Diabetes Linked to Threefold Increase in Dementia Risk

Older adults with type 1 or type 2 diabetes had a higher risk of dementia, a U.S. prospective cohort study found.

Compared with people without diabetes, older adults with type 1 diabetes had a nearly threefold higher risk for incident all-cause dementia (HR 2.82, 95% CI 2.28-3.48) over a 2.4-year follow-up period, after adjusting for sociodemographic factors. Those with type 2 diabetes had a roughly twofold increased risk (HR 2.08, 95% CI 1.87-2.31).

An estimated 64.5% of dementia cases in people with type 1 diabetes could be attributed to the condition, Jennifer Weuve, MPH, ScD, of Boston University School of Public Health, and colleagues reported in Neurology.

“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,” Weuve explained in a statement.

“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,” she added.

“Type 1 diabetes is not common, so this condition accounts for a small fraction of all dementia cases,” Weuve pointed out. “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.”

There has been “vast evidence amassed” linking diabetes and dementia risk, but few studies have quantified the risk in type 1 diabetes, the researchers noted.

“Our findings regarding type 2 diabetes are consistent with previous literature,” they wrote. Type 2 diabetes is tied to dementia risk through several mechanisms including hyperglycemia, increased beta-amyloid deposition, or comorbidities such as metabolic syndrome, hyperinsulinemia, or stroke, they explained.

In type 1 diabetes, however, hypoglycemic events may drive dementia risk by causing neuronal damage through altered glucose metabolism, insulin insufficiency, or oxidative stress and inflammation in the hippocampus.

“Although type 2 diabetes entails insulin resistance and hyperglycemia, type 1 diabetes may present a unique set of risks, in part due to the autoimmune destruction of beta cells,” Weuve’s team noted. “These mechanisms should be further explored.”

Data came from the ongoing longitudinal All of Us cohort which was started in 2017. The analysis included 283,772 participants: 5,442 individuals with type 1 diabetes, 51,511 with type 2 diabetes, and 226,819 without diabetes. Mean age was 64.6 years, 56.7% were women, 60.3% were non-Hispanic white, and 13.3% were Hispanic/Latino. Average body mass index was 29.83.

Diabetes and dementia diagnoses were determined through electronic health record data. During follow-up, 2,348 participants developed dementia. All-cause dementia included Alzheimer’s dementia, vascular dementia, and dementia of unknown etiology. Frontotemporal, Lewy body, or alcohol-related dementias weren’t included.

Both women (HR 3.04, 95% CI 2.28-4.05) and men (HR 2.59, 95% CI 1.90-3.54) with type 1 diabetes had a higher risk for dementia compared with their counterparts who had no diabetes. All race and ethnic groups with type 1 diabetes also had significantly elevated dementia risks.

Weuve and co-authors acknowledged a potential surveillance bias. Because individuals with type 1 diabetes have more frequent contact with healthcare systems, they may have been more likely to receive an earlier dementia diagnosis than others.