Longer exposure to endogenous estrogen may provide cognitive protection in women with type 2 diabetes mellitus (T2DM). A study published in Diabetes Care assessed the association of reproductive factors with dementia risk in postmenopausal women with T2DM.

The cohort included 159,751 individuals older than 40 years who underwent health examinations in 2009 using data from the National Health Information Database. Reproductive history was obtained through standardized questionnaires. All-cause dementia, Alzheimer disease, and vascular dementia were identified using diagnosis codes and prescriptions of antidementia medications. Cox proportional hazards regression models evaluated dementia risk according to reproductive lifespan, parity, and HRT duration.

Mean age was 64.5 ± 8.0 years, and mean reproductive lifespan was 33.6 ± 4.5 years. Over a median follow-up of 8.3 years, 24,218 dementia cases occurred, including 18,819 Alzheimer disease and 2,743 vascular dementia cases. A reproductive lifespan ≥40 years was associated with a hazard ratio (HR) of 0.73 (95% CI 0.69–0.78) for all-cause dementia versus <30 years. Women with parity 1 had a 27% lower dementia risk than parity 0, while HRT use for more than five years reduced risk by 17%. Comparable risk reductions were observed for both dementia subtypes.

These findings support a beneficial association between reproductive estrogen exposure and long-term cognitive outcomes in women with T2DM.