People living with diabetes may face an increased risk of developing dementia as they age, according to a large new U.S. study. The association appeared strongest among adults with type 1 diabetes, who were nearly three times as likely to develop dementia as those without diabetes. Adults with type 2 diabetes had about twice the risk.
Researchers stress that the study identified a statistical link, not proof that diabetes directly causes dementia.
The findings were published in Neurology and highlight the need for closer attention to long-term brain health in people living with diabetes.
A Growing Area of Research
Diabetes is a group of metabolic conditions involving problems with insulin production, insulin action, or both. Over time, elevated blood sugar levels can damage blood vessels and contribute to inflammation throughout the body.
Because of these effects, diabetes is often associated with multiple chronic health conditions. Scientists have long suspected that diabetes may also influence cognitive decline, though the biological pathways remain under investigation.
Most earlier studies focused on type 2 diabetes. New evidence now suggests that type 1 diabetes may play an even larger role in dementia risk than previously recognized.
Findings From a Large National Study
Researchers analyzed data from 283,772 adults age 50 and older enrolled in the All of Us Research Program, a nationwide initiative combining electronic health records with survey information to study long-term health outcomes.
Participants included:
5,442 people with type 1 diabetes
51,511 people with type 2 diabetes
226,819 people without diabetes
The average participant age was 64 years, and follow-up lasted about 2.4 years.
During that time, 2,348 participants developed dementia, including:
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 differences in age, sex, race, ethnicity, and education level, researchers estimated that people with type 1 diabetes had nearly three times the risk of dementia compared with those without diabetes. The association remained strong even after accounting for lifestyle factors such as smoking and alcohol use.
Consistent Patterns Across Groups
The increased risk linked to type 1 diabetes appeared across both men and women and across multiple racial and ethnic groups.
Women with type 1 diabetes showed slightly higher relative risk than men, although both groups demonstrated a similar overall pattern.
While type 1 diabetes accounts for fewer than 5% of diabetes cases nationwide, researchers estimate that nearly two-thirds of dementia cases among people with type 1 diabetes in the study could be related to the condition itself. Across the entire study population, however, type 1 diabetes accounted for about 3.9% of dementia cases overall.
Possible Biological Explanations
Scientists are still working to understand why diabetes may affect brain health.
Type 2 diabetes is commonly associated with insulin resistance and long-term metabolic changes that can damage blood vessels in the brain and promote abnormal protein buildup linked to Alzheimer’s disease.
Type 1 diabetes is different. It is an autoimmune condition in which the body destroys insulin-producing cells in the pancreas. People with type 1 diabetes typically require lifelong insulin therapy and may experience repeated episodes of low blood sugar.
Researchers suggest several factors that could contribute to dementia risk in type 1 diabetes, including:
recurrent hypoglycemia
chronic inflammation
oxidative stress
long-term metabolic disruption
Because people with type 1 diabetes are often diagnosed earlier in life, they may also live with the condition for many decades, increasing cumulative exposure to these effects.
However, the study was not designed to test these mechanisms directly. Additional research will be needed to confirm how they influence cognitive decline.
Improving Research Accuracy
A key feature of the study was the use of a new method to distinguish between type 1 and type 2 diabetes in large health datasets.
Diagnostic coding can sometimes overlap, particularly when people with type 2 diabetes require insulin therapy. To improve accuracy, researchers developed an algorithm based on repeated clinical documentation and validated it using self-reported diabetes type and laboratory testing of C-peptide, a marker of insulin production.
This approach allowed investigators to evaluate dementia risk separately for each diabetes subtype in a large and diverse population.
Study Limitations
Researchers note several limitations. Diagnoses of both diabetes and dementia were based on electronic health records and survey data, which may not capture every case.
People with type 1 diabetes also tend to have more frequent contact with healthcare systems, which could increase the likelihood that dementia is identified earlier.
In addition, the All of Us study population does not fully represent the entire U.S. population. For these reasons, the results should be interpreted cautiously.
Most importantly, the findings show association rather than causation.
What the Results Mean for Patients and Clinicians
As life expectancy continues to improve for people with type 1 diabetes, more individuals are reaching older ages — the period when dementia risk increases most.
Researchers say these findings support greater awareness of cognitive health as part of long-term diabetes care. In some cases, clinicians may consider monitoring memory and thinking changes more closely over time.
At the same time, an increased risk does not mean dementia is inevitable.
Health experts recommend several steps that may help lower dementia risk overall:
maintaining stable blood sugar levels
controlling blood pressure
staying physically active
following a balanced diet
maintaining a healthy weight
staying socially and mentally engaged
treating hearing problems
getting adequate sleep
avoiding tobacco use
limiting alcohol intake
preventing head injuries
Future studies will help clarify how diabetes influences brain aging and whether targeted prevention strategies can reduce dementia risk in people living with the condition.
