Married adults who take care of a spouse with dementia are about six times more likely to develop dementia themselves, according to a new 12-year-long study published Wednesday.
The researchers say they don't know what accounts for their findings but they suggest that either the stress of being a caregiver or something in the shared environment of the couple raises the risk.
For the study, published in the Journal of the American Geriatrics Society, researchers from Utah State University, Johns Hopkins and Duke University examined 2,442 married people ages 65 and older. None of the seniors had dementia at the start of the study.
They were monitored for 12 years and given comprehensive clinical assessments to diagnose dementia. During that time, 125 cases of dementia were diagnosed in husbands and 70 cases in wives and 30 cases in which both the husband and wife were diagnosed.
The analysis showed that people with a spouse with dementia were at six times higher risk of developing dementia themselves. The risk was much higher for men caring for their wives than for wives caring for their husbands.
The researchers say the increased risk they saw among caregivers was on par with the power of a gene variant, known as APOE-a4, which has been shown to increase susceptibility to Alzheimer's disease.
"On the positive side, the majority of these individuals with spouses who develop dementia did not themselves develop dementia," the lead author of the study, Dr. Maria Norton, of Utah State University, said in a news release.
She noted that the long-term nature of her team's research makes the results more reliable than earlier "snapshot" studies.
"We know that the declines in memory we saw were real and persistent, not just a point in time where they weren't performing well on tests," she says.
Norton and her colleagues speculate that the stress of caregiving might be responsible for the increased dementia risk for spouses. But she said more research is needed to identify what that mechanism might be.
"More research is needed to explore which factors distinguish those who are more vulnerable."
Johns Hopkins psychiatry professor Dr. Peter Rabins noted though that the research doesn't suggest that spouses shouldn't care for their spouses with dementia.
"Caregiving has positive aspects, as well as negative ones. If we can boost the positive aspects and reduce the negative ones, we may be able to reduce a caregiver's risk of developing dementia," Rabins said.
