Importance: Previous studies suggest that spouses of individuals with dementia may be at increased risk of developing dementia, but evidence regarding subgroup variation and absolute risk remains limited. Objective: To examine whether spouses of individuals with dementia have an increased risk of developing dementia and to assess whether this association is modified by demographic, socioeconomic, and family context factors. Design, Setting, and Participants: This nationwide population-based cohort study used Taiwan's National Health Insurance Research Database from 1998 to 2022, with follow-up through 2022. To address prior limitations of small sample size and limited subgroup evaluation, spouses of individuals with incident dementia were identified and matched 1 to 4 to unexposed controls by birth year, sex, income, and urbanicity. The analysis was conducted between July 15, 2025, and May 15, 2026. Exposure: Spousal exposure to incident dementia. Main Outcomes and Measures: Incident all-cause dementia, Alzheimer disease, and vascular dementia. Hazard ratios (HRs) and 5-year absolute risk differences were estimated using Cox regression and g-computation. Results: The matched cohort included 955 105 individuals, with 118 904 exposed women and 72 117 exposed men as well as 475 616 unexposed women and 288 468 unexposed men. The largest proportion were aged 65 to 74 years at cohort entry, for women (47 084 39.6%) and men (28 477 39.5%). Spouses of individuals with dementia had a higher risk of all-cause dementia than unexposed spouses. For women, the HR was 1.74 (95% CI, 1.70-1.78), with a 5-year adjusted risk difference of 2.75 percentage points (pp) (95% CI, 2.63-2.87 pp). For men, the HR was 1.69 (95% CI, 1.64-1.73), with a 5-year adjusted risk difference of 3.49 pp (95% CI, 3.30-3.69 pp). Similar patterns were observed in analyses of Alzheimer disease and vascular dementia. Relative risks were more prevalent at younger ages, whereas absolute risk differences increased with age. For all-cause dementia, the association was attenuated among individuals with higher income or more children. Associations were otherwise broadly similar across sex and urbanicity. Conclusions and Relevance: In this cohort study of married individuals in Taiwan, spouses of individuals with dementia had a higher risk of dementia than unexposed spouses. The association varied across family and socioeconomic contexts, highlighting the relevance of household context in dementia risk assessment.
Wang et al. (Mon,) studied this question.