BOSTON — People with type 1 diabetes face nearly three times the risk of developing dementia compared with those without diabetes, according to a large new U.S. cohort study published March 18, 2026, in *Neurology*, the medical journal of the American Academy of Neurology. The findings highlight a stronger association for type 1 than for type 2 diabetes and raise concerns as advances in care allow more individuals with type 1 to reach older ages.

type 1 and type 2 diabetes
type 1 and type 2 diabetes

Led by Jennifer Weuve, MPH, ScD, of Boston University School of Public Health, the research drew on data from the National Institutes of Health's All of Us Research Program, analyzing electronic health records and surveys from 283,772 adults aged 50 and older (mean age 65, 57% women). Of these, 5,442 (1.9%) had type 1 diabetes and 51,511 (18.2%) had type 2. An algorithm distinguished diabetes types, validated against self-reports and C-peptide levels.

Over an average 2.4-year follow-up (2017–2023), 2,348 participants (0.83%) developed dementia. Incidence rates were 2.6% among those with type 1 diabetes, 1.8% with type 2 and 0.6% without diabetes. After adjusting for sociodemographic factors — age, sex, race/ethnicity, education and household income — the hazard ratio for all-cause dementia was 2.82 (95% CI 2.28-3.48) for type 1 diabetes and 2.08 (95% CI 1.87-2.31) for type 2, relative to no diabetes.

The elevated risk held across genders, racial/ethnic groups and persisted even after accounting for lifestyle factors like smoking and alcohol use in supplementary analyses. Researchers estimated that about 65% of dementia cases among people with type 1 diabetes could be attributed to the condition itself.

"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 said 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."

The study adds to prior evidence, including a 2025 Swedish nationwide registry analysis of over 43,000 people with type 1 diabetes showing a roughly twofold higher risk (HR 2.02 for all-cause dementia) over 14 years, with particularly elevated vascular dementia (HR 3.73). That research identified additional risk factors like higher HbA1c, systolic blood pressure, cardiovascular history, stroke/transient ischemic attack, lower education, single status and longer diabetes duration.

Mechanisms linking diabetes to dementia remain under study. Chronic hyperglycemia may damage blood vessels and promote inflammation, contributing to vascular dementia and cognitive decline. Hypoglycemia episodes, more common in type 1 due to insulin therapy, could also play a role by causing brain injury over time. Type 1's autoimmune nature and earlier onset might amplify long-term brain effects compared with type 2, often tied to insulin resistance and metabolic syndrome.

The U.S. study's shorter follow-up contrasts with longer-term cohorts but benefits from diverse representation through All of Us, aiming to address underrepresentation in research. Limitations include reliance on electronic records (potential misclassification), short observation period (limiting detection of slower-onset dementias) and exclusion of some dementia subtypes like frontotemporal or Lewy body.

Experts emphasize the association does not prove causation. "This study shows an association and does not prove that diabetes causes dementia," the American Academy of Neurology noted in its release. Researchers called for further investigation into mechanisms, including potential roles of glycemic variability, insulin therapy and neuroprotective strategies.

For patients and clinicians, the findings underscore proactive brain health measures. Good glycemic control, blood pressure management, cardiovascular risk reduction, regular cognitive screening and lifestyle interventions — exercise, diet, social engagement — may help mitigate risks. As type 1 populations age, with more reaching 65+, targeted prevention becomes critical.

The results align with growing recognition of diabetes as a modifiable dementia risk factor. Previous meta-analyses and cohorts have linked type 2 to 50-100% higher odds, but type 1 data were scarcer until recent large-scale efforts.

As the global population with type 1 diabetes grows older thanks to better management, studies like this highlight the need for integrated care addressing both metabolic and neurological health. Future research may explore whether advanced insulin pumps, continuous glucose monitoring or emerging therapies reduce long-term brain risks.