In a finding that seems counter-intuitive, researchers have discovered that an individual’s risk for dementia rises if their spouse also has dementia.
Having a spouse with dementia resulted in a six-fold increased risk of developing the condition. Men’s risk increases almost 12-fold, as compared to a four-fold increase in women.
“Given the significant public health concern of Alzheimer’s disease and other dementias, and the upcoming shift in population age composition, continued research into the causes of dementia is urgent,” noted Dr. Maria Norton of Utah State University, lead author of the new study.
Informal dementia caregiving for a spouse is a natural marital obligation, and spousal caregivers often report positive feelings toward caregiving, yet it is difficult, requiring time, energy and usually physical exertion. Dementia caregivers have been shown to provide more assistance, and to report more personal sacrifices and stress, than those who care for physically-impaired elderly without dementia.
While there are many published studies showing that dementia caregivers are at higher risk for health problems and depression, none have examined risk for dementia in the caregiver.
The new research examined 2,442 subjects (1,221 married couples) aged 65 and older from Northern Utah without dementia at onset. They were studied for up to 12 years to monitor for onset of dementia in husbands, wives or both.
During this time, 125 cases of dementia only in the husband were diagnosed, 70 only in the wife, and 30 where both spouses were diagnosed (60 people).
The researchers also adjusted for socioeconomic status, a significant predictor of many health-related outcomes including dementia to control for shared environmental exposures that might influence risk for dementia in both spouses.
The results showed that incident dementia was significantly associated with older age, and having a spouse with dementia. Participants with a spouse who developed dementia were at a six times increased risk of developing dementia, net of the effect of age, gender, APOE genotype, and socioeconomic status, with higher risk in men (11.9) than women (3.7).
Norton and her colleagues don’t yet know what is at the root of the hike in risk. It’s entirely possible that there are environmental factors that we don’t yet know about, Norton said. “Controlling for economic status is not the same as controlling for the 5,000 things that people can share,” she noted.
“It’s possible that we’ll find that there is something that the caregivers who developed dementia had in common, such as a particular personality trait or their coping styles. Or, maybe it isn’t as much about the caregiver so much as it is about the spouse who gets dementia first: how rapidly they decline, whether they have delusions. Not all dementias are the same. Some might be more stressful to the caregiver.”
“Future studies are needed to determine how much of this association is due to caregiver stress compared to a shared environment,” said Norton.
“On the positive side, the majority of these individuals, with spouses who develop dementia, did not themselves develop dementia, therefore more research is needed to explore which factors distinguish those who are more vulnerable.”
The study was published today in the Journal of the American Geriatrics Society.