Reproductive Lifespan and Reproductive Factors in Relation to Dementia Risk in Postmenopausal Women With Type 2 Diabetes.

OBJECTIVE

Endogenous estrogen exposure has been linked to a reduced risk of cognitive decline. Our study examined the influence of reproductive factors on the risk of dementia among women with diabetes.

RESEARCH DESIGN AND

METHODS

We identified 159,751 postmenopausal women with type 2 diabetes aged over 40 years who underwent health examinations in 2009 from the National Health Information Database. Data on reproductive factors were obtained using self-administered questionnaires. Incident dementia was determined by diagnosis codes and records of antidementia medication prescriptions. Cox proportional hazards regression analyses estimated the risk of all-cause dementia, Alzheimer disease, and vascular dementia according to reproductive factors such as reproductive lifespan, parity, and hormone replacement therapy (HRT) use.

RESULTS

The mean age was 64.5 ± 8.0 years, and the mean reproductive lifespan was 33.6 ± 4.5 years. Over a median follow-up of 8.3 years, 24,218 cases of all-cause dementia were identified (18,819 cases of Alzheimer disease, 2,743 cases of vascular dementia). Compared with a reproductive lifespan of <30 years, ≥40 years was associated with lower risk of all-cause dementia (hazard ratio 0.73; 95% CI 0.69-0.78). Women with parity 1 had a 27% lower risk of all-cause dementia compared with women with parity 0, and women who used HRT for more than 5 years had a 17% lower risk compared with those who did not use HRT. Comparable effects were found for both Alzheimer disease and vascular dementia.

CONCLUSIONS

A longer reproductive lifespan was linked to a reduced risk of dementia in postmenopausal women with type 2 diabetes.