Résumé
INTRODUCTION Marital status is a potential risk/protective factor for adverse health outcomes. This study tested whether marital status was associated with dementia risk in older adults. METHODS Participants ( N = 24,107; Mean age = 71.79) were from the National Alzheimer's Coordinating Center. Cox regressions tested the association between baseline marital status and clinically ascertained dementia over up to 18 years of follow‐up. RESULTS Compared to married participants, widowed (hazard ratio [HR] = 0.73, 95% confidence interval [95% CI] = 0.67–0.79), divorced (HR = 0.66, 95% CI = 0.59–0.73), and never‐married participants (HR = 0.60, 95% CI = 0.52–0.71) were at lower dementia risk, including for Alzheimer's disease and Lewy body dementia. The associations for divorced and never married remained significant accounting for demographic, behavioral, clinical, genetic, referral source, participation, and diagnostic factors. The associations were slightly stronger among professional referrals, males, and relatively younger participants. DISCUSSION Unmarried individuals may have a lower risk of dementia compared to married adults. The findings could indicate delayed diagnoses among unmarried individuals or challenge the assumption that marriage protects against dementia. Highlights Widowed, divorced, and never‐married older adults had a lower dementia risk, compared to their married counterparts. Unmarried older adults were also at a lower risk of Alzheimer's disease and Lewy body dementia, with a pattern of mixed findings for frontotemporal lobar degeneration, and no associations with risk of vascular dementia or mild cognitive impairment. All unmarried groups were at a lower risk of progression from mild cognitive impairment to dementia. There was some evidence of moderation by age, sex, and referral source. However, stratified analyses showed small differences between groups, and most interactions were not significant, suggesting that the role of marital status in dementia tends to be similar across individuals at different levels of dementia risk due to education, depression, and genetic vulnerability.