Spouses who care for partners with dementia are six times more likely to develop the disorder too, compared to healthy elderly couples, according to a Utah study.
It's possible that the incredible stress of watching their partner deteriorate, as well as taking care of their physical and emotional needs, impairs the brain of the caring spouse, according to the study. There also may be something in the couple's shared environment -- their diet and exercise patterns or chemical exposures -- that explains the shared disease.
Past studies have linked dementia caregiving to depression, physical and cognitive problems and death. This study, published Wednesday in the Journal of the American Geriatrics Society , is thought to be the first to look at the link with developing dementia.
Risk of dementia grows as people age --- it's up to 50 percent after age 85 -- and if they have a particular genetic mutation. Even after controlling for those factors, caregiving remained a risk, the study showed.
"You still have a separate, unique, independent association in its own right. It's not their age or their gender or their genes," said Maria Norton, the study's principal investigator and an associate professor at Utah State University's Department of Family Consumer and Human Development.
Researchers used data from the Cache County Study on Memory Health and Aging, an ongoing study started in 1995 of people age 65 and older in the northern Utah county.
Of the 1,221 married couples included in the study, there were 195 cases of dementia in only the husband or wife, and 30 cases of dementia in both spouses.
Norton said the study is just a first step; she would like to see what made the difference between the caregivers who developed dementia and those who didn't.
Maybe they have different ways of coping with stress, different support systems or different underlying physical and mental health, she said.
Jack Jenks, executive director of the Alzheimer's Association's Utah Chapter, wasn't surprised to hear the study results; he's seen caregivers turn into patients.
He estimates there are 100,000 dementia caregivers in Utah, mainly spouses or children.
The local chapter emphasizes help for them as much as the person with the disease, offering support groups and respite care.
And they need help: Jenks cites national statistics showing there is a one in four chance that a caregiver over age 65 will end up in the emergency room for their own health problems in any six-month period.
"There is more evidence than ever that caregivers are often dying before the person with dementia just because of the stress," he said. "We call it the 36-hour-day. You never get a break."
Rodent studies have found chronic stress damages the hippocampus, the region in the brain responsible for forming memories.
A dementia caregiver faces different challenges than a spouse caring for a loved one with a physical condition, Norton said.
"This is a continual, gradual decline," Norton said. "Eventually it gets to the point where they may not recognize you. You have this grief process too -- grieving the loss of the relationship."
The study was funded through the National Institute on Aging and included researchers from six other institutions.
An estimated 32,000 Utahns have the disease. That number is projected to grow to 50,000 in 2025 -- the highest percentage increase expected in the nation, at 127 percent.
Source: 2010 Alzheimer's Disease Facts and Figures, from the Alzheimer's Association.