Study Links Type 1 Diabetes to Higher Dementia Risk

People living with diabetes may face a higher risk of developing dementia as they age, according to a large new U.S. study. The link was strongest for type 1 diabetes: those adults were nearly three times as likely to develop dementia as people without diabetes. Adults with type 2 diabetes had about twice the risk.

One important caveat up front: the study found a statistical association, not proof that diabetes directly causes dementia.

The findings were published in Neurology, and they underline the need to watch long-term brain health in people with diabetes.

A Growing Area of Research

Diabetes is a group of metabolic conditions marked by problems with insulin production, insulin action, or both. Over time, high blood sugar can damage blood vessels and drive inflammation throughout the body — which is why diabetes so often travels with other chronic conditions.

Scientists have long suspected diabetes also feeds cognitive decline, though the exact biology is still being mapped. Most earlier work focused on type 2 diabetes; this study suggests type 1 may play an even bigger role in dementia risk than previously recognized.

Findings From a Large National Study

Researchers analyzed data from 283,772 adults age 50 and older in the All of Us Research Program, a nationwide effort that pairs electronic health records with survey data. Participants broke down into:

• 5,442 people with type 1 diabetes
• 51,511 people with type 2 diabetes
• 226,819 people without diabetes

The average age was 64, with follow-up of about 2.4 years. In that window, 2,348 participants developed dementia:

• 2.6% of those with type 1 diabetes
• 1.8% of those with type 2 diabetes
• 0.6% of those without diabetes

After adjusting for age, sex, race, ethnicity, and education, people with type 1 diabetes had nearly three times the dementia risk of those without diabetes — and the link held even after accounting for smoking and alcohol use.

Consistent Patterns Across Groups

The elevated type 1 risk showed up across men and women and across racial and ethnic groups. Women with type 1 diabetes had a slightly higher relative risk than men, though the overall pattern was similar.

Type 1 diabetes makes up fewer than 5% of all diabetes cases, yet researchers estimate that nearly two-thirds of dementia cases among people with type 1 diabetes in the study could be tied to the condition itself. Across the whole population, type 1 accounted for about 3.9% of dementia cases overall.

Possible Biological Explanations

Why diabetes affects the brain is still being worked out. Type 2 diabetes is closely tied to insulin resistance and long-term metabolic changes that can damage brain blood vessels and encourage the abnormal protein buildup seen in Alzheimer’s disease.

Type 1 diabetes is a different beast — an autoimmune condition in which the body destroys the insulin-producing cells of the pancreas, requiring lifelong insulin therapy and sometimes repeated episodes of low blood sugar. Researchers point to several factors that could raise dementia risk here:

• recurrent hypoglycemia
• chronic inflammation
• oxidative stress
• long-term metabolic disruption

Because type 1 is usually diagnosed early in life, people often live with it for decades, piling up cumulative exposure to these effects. The study wasn’t built to test these mechanisms directly, though, so confirming them will take more research.

Sharper Sorting of Diabetes Type

A standout feature of the study was a new way to separate type 1 from type 2 diabetes in large datasets. Diagnostic codes can blur together — especially when people with type 2 also use insulin. To tighten accuracy, the team built an algorithm based on repeated clinical records and validated it against self-reported diabetes type and C-peptide testing, a marker of insulin production. That let them assess dementia risk separately for each subtype across a large, diverse population.

Study Limitations

Several caveats apply. Both diabetes and dementia diagnoses came from health records and surveys, which may miss cases. People with type 1 diabetes also tend to see clinicians more often, which could mean dementia is caught earlier in that group. And the All of Us population doesn’t fully mirror the U.S. as a whole. Most importantly, the results show association, not causation.

What It Means for Patients and Clinicians

As people with type 1 diabetes live longer, more are reaching the ages when dementia risk climbs — so the researchers argue cognitive health deserves a place in long-term diabetes care, with closer attention to memory and thinking over time in some patients.

Higher risk doesn’t make dementia inevitable, though. Experts point to several habits that may help lower risk overall:

• keeping blood sugar stable
• controlling blood pressure
• staying physically active
• eating a balanced diet
• maintaining a healthy weight
• staying socially and mentally engaged
• treating hearing problems
• getting enough sleep
• avoiding tobacco
• limiting alcohol
• preventing head injuries

Future studies will help clarify how diabetes shapes brain aging — and whether targeted prevention can actually cut dementia risk for people living with the condition.