Older adults whose spouses have dementia are on average six times more likely to develop the condition than seniors whose partners are not afflicted, according to a recent study.
The danger is several-fold higher for men than women, found the study, published in the Journal of the American Geriatrics Society.
Dementia is not a disease, but covers a group of symptoms - including memory loss, agitation, mood swings and changes in personality - caused by disorders that affect the brain, such as Alzheimer's.
Caring for persons with dementia can be extremely stressful, especially for a spouse with deep emotional ties to someone whose behaviour may become suddenly strange or even abusive.
Earlier research has shown that dementia caregivers are at a higher risk for health problems, including depression, than counterparts who provide for individuals who are physically but not mentally impaired.
But the new study, led by Maria Norton of Utah State University, is the first to examine risk for dementia in caregivers.
A total of 2,442 subjects without dementia - 1,221 married couples - aged 65 and older were studied for up to 12 years to monitor for the onset of symptoms.
Among the couples, 125 cases were diagnosed in the man alone, and 70 in the woman alone. In addition, there were 30 couples in which both persons were affected.
Even with confounding influences factored out, the risk of onset symptoms for participants with a spouse who developed dementia increased nearly 12-fold for men and 3.7 fold for women.
"Given the significant public health concern of Alzheimer's disease and other dementias, and the upcoming shift in population composition, continued research in the causes of dementia is urgent," Norton said in a press release.
"Future studies are needed to determine how much off this association is due to caregiver stress compared to a shared environment," she said.