Does dementia risk differ between type 1 mellitus (T1DM) and type 2 diabetes mellitus (T2DM)? A prospective cohort study published in Neurology evaluated associations between diabetes type and incident dementia using linked electronic health records.

The analysis included 283,772 adults aged 50 years or older from the All of Us cohort. Participants completed baseline surveys, and electronic health record data were available through October 2023, with a mean follow-up of 2.4 years. An algorithm based on the number of type 1 diabetes encounters was developed and validated using self-reported diabetes type and C-peptide values to classify participants as having no diabetes, T1DM, or T2DM.

Dementia was identified using diagnostic codes from ICD-9, ICD-10, and Systematized Nomenclature of Medicine records. Using a threshold of at least one T1DM encounter, 5,442 participants were classified as having T1DM. Compared with participants without diabetes, those with T1DM had higher dementia incidence (hazard ratio [HR] 2.82; 95% confidence interval [CI] 2.28-3.48). Participants with T2DM also had elevated dementia incidence (HR 2.08; 95% CI 2.87-2.31).

Findings were consistent across sex, race, and ethnicity strata. Overall, diabetes was associated with higher dementia incidence, with a higher risk observed in T1DM compared with T2DM.