Spouses of individuals with dementia may have increased risk for cognitive disorders

Identifying and addressing risk factors for cognitive disorders shared within couples may reduce the risk for these disorders in the spouses of those with dementia, according to results of a prospective cohort study in JAMA Network Open.

“Spouses generally share a common environment, and many studies have investigated spousal concordances for factors such as lifestyle and physical and psychological health,” Hee Won Yang, MD, of the department of neuropsychiatry at Seoul National University Bundang Hospital in South Korea, and colleagues wrote. “These factors, which are concordant within couples, are known to be associated with a risk of dementia or cognitive decline and are also negatively associated with spousal cognitive disorders. Therefore, these factors may mediate cognitive disorders and changes in cognitive functions that correlate within couples. In addition, because most of these factors are modifiable and can contribute to a reduction in the risk of dementia, early detection and correction within couples is important in preventing dementia.”

To Yang and colleagues’ knowledge, no direct investigation has examined the mediating effects of shared risk factors within couples on the risk for cognitive impairment linked to spousal cognitive disorders. To address this research gap, they conducted a nationwide, multicenter, community-based study in which they followed 784 participants (39.2% women; mean age, 74.8 years) from the Korean Longitudinal Study on Cognitive Aging and Dementia (KLOSCAD) and a cohort of their spouses (KLOSCAD-S) (60.8% men; mean age, 73.6 years) every 2 years until Dec. 31, 2020. They defined the cognitive disorder of a souse as mild cognitive impairment or dementia. As the main outcome, Yang and colleagues used the mediating roles of factors shared within couples on the link between one spouse’s cognitive disorder and the other’s risk for cognitive disorders, examined via structural equation modeling.

Results showed an association between the cognitive disorder of the KLOSCAD participants and a nearly two-fold increased risk for cognitive disorder of their spouses in the KLOSCAD-S cohort (OR = 1.74; 95% CI, 1.12-2.69). Mediating factors for the link between cognitive disorder in the KLOSCAD participants and their spouses’ risk for cognitive disorder included history of head injury (beta = 0.5; 95% CI, 0.09-0.9) and age (beta = 2.57; 95% CI, 1.37-3.76). Researchers noted a mediating effect of physical inactivity on the association through major depressive disorder, as well as similar mediating effects of these factors on the association between spousal cognitive disorder and cognitive functions, including memory and executive function.

“This cohort study is, to our knowledge, the first to demonstrate that shared environments within couples may underlie shared cognitive disorders and cognitive performance within couples,” Yang and colleagues wrote. “Identification and intervention of the shared risk factors of dementia within couples may reduce the risk of cognitive disorders in the spouses of people with dementia.”

In a related editorial, Peter P. Vitaliano, MS, PhD, of the department of psychiatry and behavioral sciences at the University of Washington School of Medicine, highlighted a limitation of the study and a potential path forward for future research in this area.

“Yang [and colleagues] discuss literature on caregiver cognitive problems in detail, but their study has limited data on the extent to which spouses are caregivers and, if so, their specific stressors and demands and responses to caregiving (eg, metabolic dysregulation) and to other major life stressors,” Vitaliano wrote. “All of these variables are relevant to cognitive function. In sum, the study by Yang [and colleagues] makes a major contribution to knowledge about the joint prevalence and risks of cognitive disorders in married couples and the work highlights many areas in which to extend this work as it relates to previous research.”