One Partner’s Dementia May Predict the Other’s Future Risk

Spouses of people with dementia had a higher risk of developing dementia themselves, a matched cohort study of nearly 1 million married people in Taiwan showed.

Compared with unexposed spouses, both husbands and wives of dementia patients had a higher risk of all-cause dementia, corresponding to roughly three additional cases per 100 spouses over 5 years, said Chi-Shin Wu, MD, PhD, of the National Health Research Institutes in Zhunan Town, and co-authors.

For women, the hazard ratio was 1.74 (95% CI 1.70-1.78), with a 5-year adjusted risk difference of 2.75 percentage points, the researchers reported in JAMA Network Open. For men, the hazard ratio was 1.69 (95% CI 1.64-1.73), with a 5-year adjusted risk difference of 3.49 percentage points.

Similar trends emerged for both Alzheimer’s disease and vascular dementia. Younger people had higher relative risks, but older age groups experienced greater absolute risk differences. For all-cause dementia, higher income and having more children buffered the association.

“This study moves dementia risk assessment beyond the individual to the household,” Wu noted.

“The association likely reflects several overlapping factors, including similarities between partners before marriage, decades of shared lifestyle, and the burden of caring for a spouse with dementia,” he told MedPage Today. “Because we could not measure caregiving directly, our findings should not be interpreted as showing that caregiving causes dementia,” he pointed out.

“For clinicians, a dementia diagnosis in one spouse may be an opportunity to consider the health of the other spouse as well, including cognition, mood, sleep, cardiovascular risk factors, and access to family or respite support,” Wu suggested.

“The main message is awareness rather than alarm: spouses should not assume that they will develop dementia, but their own health should not be overlooked while they are supporting their partner,” he said.

Earlier research documented poorer cognitive performance, accelerated cognitive decline, and higher dementia risk in the spouses or caregivers of dementia patients. A study in Cache County, Utah, for example, reported a 600% greater risk of dementia in spouses of people with dementia. Research in Korea showed that if an individual had a cognitive disorder, a spouse’s risk of mild cognitive impairment or dementia doubled.

Many of these analyses involved relatively small or regional samples, Wu and co-authors noted. A literature review based on earlier work suggested modifiable risk factors for dementia that, if unchecked, could compromise caregivers’ cognition and well-being.

Wu and colleagues studied a matched cohort of 955,105 married people that included 118,904 women and 72,117 men whose partners had dementia, as well as 475,616 unexposed women and 288,468 unexposed men.

Couples were born between 1930 and 1969 and had a single recorded marriage and one opposite-sex spouse. The median follow-up was 7.0 years for women exposed to dementia and 5.5 years for men.

The cohort was drawn from Taiwan’s National Health Insurance Research Database from 1998 to 2022. Covariates included age, income, urbanicity, number of children, and healthcare use in the preceding year.

The largest proportion — 39.6% of women and 39.5% of men — was 65 to 74 years old at study entry. Most people lived in urban areas, and nearly half were in the lowest-income category.

Two earlier studies suggested that husbands of dementia patients were particularly vulnerable, but in this analysis, the relationship between spousal dementia and subsequent risk was broadly similar in women and men, Wu and co-authors observed. “Overall, these findings suggest that sex differences in spousal dementia risk are modest and may largely reflect differences in age structure and caregiving context rather than intrinsic biological susceptibility,” they wrote.

Individuals with fewer children were more likely to be in the lowest-income group, suggesting smaller family size might partly reflect broader socioeconomic disadvantage, they added.

Dementia outcomes were based on administrative claims and may have been misclassified, the researchers acknowledged. Marital relationships were from registry records that do not fully capture changes like divorce, they noted. The prevalence of divorce among middle-age and older adults was about 8% in Taiwan in 2015, Wu and colleagues said.