AbstractBackgroundMenopause‐related estrogen depletion is linked to greater vascular risk, Alzheimer’s disease (AD) pathology, and dementia risk in women. Age‐at‐menopause and vascular risk may together influence the likelihood of developing AD in women. We investigated whether earlier menopause and elevated vascular risk independently or synergistically contribute to cognitive decline in postmenopausal women compared to men.MethodWe used data from the Canadian Longitudinal Study on Aging. We included 7,678 postmenopausal women (mean age = 64.6±8.49 years, mean age‐at‐menopause = 50.1±5.02 years) and 7,678 age‐matched men (mean age = 64.6±8.49 years). Sex was operationalized using self‐reported sex at birth. Vascular risk was calculated using a summary score tallying the presence/absence of hypertension, diabetes, smoking, obesity, cardiovascular disease, and stroke. Participants completed cognitive assessments at baseline and 3‐year follow‐up. Self‐reported age‐at‐menopause was categorized into tertiles: early (<49), average (49‐52), and late (>52). Linear models tested independent and interactive effects of age‐at‐menopause and vascular risk on 3‐year cognition, adjusting for baseline cognition, baseline age, education, APOE4, and test language (English/French).ResultIn women, vascular risk and age‐at‐menopause were independently associated with cognitive decline (vascular risk: β = ‐0.107, p<.001). Relative to average age‐at‐menopause, early menopause was associated with greater cognitive decline (β = ‐0.026, p = .03), whereas late menopause was associated with less decline (β = 0.025, p = .04). In men, vascular risk was also associated with greater cognitive decline (β = ‐0.112, p<.001). Next, we examined synergistic effects of age‐at‐menopause and vascular risk in postmenopausal women. Early (vs. average) menopause and elevated vascular risk interacted to accelerate cognitive decline (β = ‐0.224, p = .002). There was no interaction between late (vs. average) menopause and vascular risk (β = ‐0.073, p = .3). In a model comparing sexes (Figure 1), vascular risk was more strongly associated with cognitive decline in women with early menopause compared to men (β = ‐0.127, p = .03). In women with average or late menopause, associations of vascular risk with cognitive decline did not significantly differ from men (average: β = ‐0.010, p = .07; late: β = ‐0.024, p = .7). Sensitivity analyses additionally adjusting for physical activity, race/ethnicity, depression, alcohol, and hormone therapy yielded similar results.ConclusionEarly menopause and vascular processes may synergistically contribute to increased AD risk in women. These findings have implications for sex‐specific dementia prevention strategies.