A large study from Taiwan has found that when one spouse develops dementia, their partner is significantly more likely to receive the same diagnosis. Researchers analysed health records from nearly one million married adults enrolled in the country's national health insurance programme between 1998 and 2022.
The study compared over 190,000 people whose spouse had a new dementia diagnosis with more than 760,000 who did not have dementia or a spouse with dementia. Over five years, around 6.5% of women whose partner had dementia were diagnosed themselves, compared with 3.7% of women whose spouse did not. For men, the figures were 9.2% and 5.8%, representing roughly three additional dementia cases per 100 people.
Women whose partners developed dementia had a 74% higher relative risk of developing dementia, while for men the increase was 69%. However, the study does not suggest that dementia is contagious. Researchers point to shared environments, lifestyles, and caregiving stress as possible explanations. Partners often accumulate similar health profiles over decades, and caring for a spouse with dementia can lead to chronic stress, disrupted sleep, and social isolation, all linked to poorer cognitive outcomes.
The study accounted for many established risk factors, including high blood pressure, diabetes, depression, and anxiety, but could not identify the exact mechanisms. The authors note that assortative mating—where people choose partners similar to themselves—may also play a role. The findings highlight the need to consider couple-level factors in dementia risk reduction strategies.
