Insulin-Dependent Diabetes Linked to Higher Risk of Dementia

A large study is adding to growing evidence that diabetes may significantly impact long-term brain health. Investigators found that people with diabetes, particularly those requiring insulin treatment, had a substantially higher risk of developing dementia, including Alzheimer’s disease and vascular dementia, compared with people without diabetes.

“This is surprising because it suggests that not all types of diabetes [carry] the same risk, and that people with more intensive or insulin-dependent treatment may be particularly vulnerable to cognitive decline,” said lead investigator Ji Eun Jun, M.D., a professor from Kyung Hee University Hospital at Gangdong in Seoul, South Korea.

The study analyzed health data from more than 1.3 million adults aged 40 years and older in South Korea between 2013 and 2024. None of the participants had dementia at the beginning of the study. Researchers then tracked participants over time to see who later developed cognitive decline or dementia.

Participants were divided into four groups: people without diabetes, people with Type 2 diabetes treated with oral medications, people with Type 2 diabetes requiring insulin therapy and people with Type 1 diabetes. The team adjusted for a number of other health and lifestyle factors, including age, smoking, alcohol use, exercise habits and underlying medical conditions.

The results showed a clear pattern: Dementia risk increased alongside diabetes severity and treatment intensity.

Among people without diabetes, the dementia rate was relatively low. However, people with type 2 diabetes treated with oral medications had about a 29% higher risk of developing dementia. The risk rose dramatically in patients with insulin-treated type 2 diabetes, who had more than double the risk compared to people without diabetes.

The highest dementia risk was seen in people with Type 1 diabetes. Their risk of developing dementia was more than twice as high as that of nondiabetic participants, and similar to the risk seen in insulin-treated Type 2 diabetes.

Importantly, investigators observed similar trends across multiple forms of dementia, including Alzheimer’s disease, the most common form of dementia, and vascular dementia, which is linked to impaired blood flow to the brain.

“Recognizing diabetes as a potential risk factor for brain health and not just a metabolic condition could help identify a group of patients who may benefit from earlier monitoring for cognitive decline,” noted Jun. “Improving long-term glucose control and reducing large fluctuations in glucose levels could play a role in lowering dementia risk.”

Frequent swings in blood sugar, including episodes of very high or very low glucose levels, may place additional stress on the brain. The findings suggest that insulin-requiring diabetes may represent a particularly high-risk form of the disease when it comes to cognitive health.

The findings highlight the importance of proactive diabetes management, not only for heart, kidney and eye health, but also for protecting brain function as people age.

The study underscores the potential value of earlier cognitive screening for people living with diabetes, especially those requiring insulin therapy, so that memory or thinking problems can be identified and addressed sooner.

“Our findings may be partly explained by recurrent hypoglycemia and greater glucose fluctuations in insulin-treated patients, thus we are planning further studies to better understand these mechanisms,” Jun concluded. “Ultimately, we hope to identify high-risk patients and determine whether improving glucose stability can help prevent dementia.”