Individuals diagnosed with type 2 diabetes at a younger age face a greater risk of developing dementia compared to those diagnosed later in life, according to research conducted by experts at the NYU Rory Meyers College of Nursing.

“Our study indicates that early-onset type 2 diabetes may have cognitive consequences. It highlights the need for prevention strategies for dementia that take both diabetes and obesity into account,” said Xiang Qi, assistant professor at NYU Meyers and the lead author of the study.

Type 2 diabetes is a recognized risk factor for dementia. While the exact mechanisms behind this connection are not completely understood, researchers believe that certain characteristics of diabetes—such as high blood sugar levels, insulin resistance, and inflammation—may contribute to the onset of dementia in the brain.

Type 2 diabetes, once common among older adults, is now increasingly seen in younger individuals. Currently, one in five people with type 2 diabetes globally is under 40 years old.

To investigate how the timing of a type 2 diabetes diagnosis is associated with the risk of developing dementia, a research team analyzed data from the Health and Retirement Study, conducted by the University of Michigan Institute for Social Research. The study, published in PLOS ONE, included 1,213 U.S. adults aged 50 and older who had type 2 diabetes confirmed by blood tests and did not have dementia when they entered the study. The participants were followed for up to 14 years, during which 216 individuals (17.8%) developed dementia, as determined by follow-up telephone interviews.

The researchers found that adults diagnosed with type 2 diabetes at younger ages were at increased risk for developing dementia compared to those diagnosed at 70 years or older. Adults diagnosed with diabetes before age 50 were 1.9 times as likely to develop dementia as those diagnosed at 70 and older, while those diagnosed between 50-59 years were 1.72 times as likely and those diagnosed between 60-69 years were 1.7 times as likely.

Using linear trend tests, the researchers found a graded association between age at diagnosis and dementia risk: for each year younger a person is at the time of their type 2 diabetes diagnosis, their risk for developing dementia increases by 1.9%.

“While we do not know for sure why an earlier diabetes diagnosis would increase the risk for dementia, prior studies show that people diagnosed with type 2 diabetes in mid-life may experience more vascular complications, poor blood sugar control, and insulin resistance—all of which are known risk factors for cognitive impairment,” said Bei Wu, the Dean’s Professor in Global Health and vice dean for research at NYU Meyers and the study’s senior author.

In addition, obesity appeared to influence the relationship between type 2 diabetes and dementia. Individuals with obesity who were diagnosed with type 2 diabetes before age 50 had the highest dementia risk in the study.

The researchers note that this greater understanding of the connection between diabetes onset, obesity, and dementia may help inform targeted interventions to prevent dementia.

“Our study highlights the importance of one’s age at diabetes diagnosis and suggests that specifically targeting obesity—whether through diet and exercise or perhaps medication—may play a role in staving off dementia in younger adults with diabetes,” said Wu.