"It is incredibly ironic, but also, it makes sense," says study researcher Peter P. Vitaliano, PhD, an adjunct professor and director of the Stress and Coping Project at the University of Washington, Seattle.
Spousal caregivers of dementia patients "have been married for, on average, 30 years in the studies," he says, "So there is all of that shared lifestyle. And then on top of it, you have all the things that happen after you become a caregiver."
The study is published in the Journal of the American Geriatrics Society.
The burdens of caregiving include many things that have been shown to increase the risk of cognitive decline, including chronic stress, social isolation, depression, decreased physical activity, and a shift in eating habits toward more fast food and processed foods.
Studies have shown, for example, that caregivers of Alzheimer's disease patients had lower scores on tests that measure attention, visual processing speeds, and memory than adults of the same age who were not caregivers. Studies also show that greater distress -- including disturbed sleep and lack of positive experiences -- appeared to account for those differences.
In 2004, Harvard researchers reported that older women who took care of a disabled or ill spouse were 31% more likely to have a low score on a standard test for cognitive function compared to women of the same age who were not caregivers.
And a study published in 2010, which followed more than 1,200 older married couples in rural Utah for 12 years, found that spouses of husbands or wives that developed dementia had a 600% greater risk of developing dementia themselves.
"It's terrifying," says Leah Eskenazi, a social worker who is director of operations and planning for the nonprofit Family Caregiver Alliance in San Francisco. "People put their lives on hold to care for somebody else, to care for a spouse. And to think that doing that puts them at risk for being in the same situation, and they see the person declining -- especially with dementia -- it's a scary disease."
Experts stress, however, that many of the lifestyle factors that have been shown to lead to cognitive decline can be changed and that doing so may help to reduce the risks of dementia and other ailments linked to caregiving, like heart disease and depression.
"We don't know anything about causality at this point," says Vitaliano. For example, he says, researchers can't say whether depression pushes caregivers into cognitive decline or whether dementia that's already there, but perhaps not as advanced as in a diagnosed spouse, may be contributing to depression.
"Like in a lot of epidemiology, these are associations and we need to understand them because they have great implications."
Shared Habits of Married Couples
Married couples may have shared years of eating, drinking, and exercise habits, Vitaliano says, all factors that are thought to play a role in the development of dementia.
Their relationship style, whether it was contentious or peaceful, may also play a role in overall stress and later brain function, as could a couple's social habits, whether they were TV-watching couch potatoes or enjoyed hobbies that kept them intellectually stimulated, like a regular bridge night.
After one spouse is diagnosed, the other often finds that the life they once knew disappears.
"What happens is people stop coming over, your friends, once the diagnosis occurs," Vitaliano says.
And wives or husbands that care for a spouse with depression soon find themselves in the midst of a full-time job.
Caregivers of dementia patients provide an average of 35 hours of direct care per week, one study in the review found.
That care is often boring and stressful, contributing to the risk for depression and loneliness, the review finds.
Depression and chronic stress have been strongly associated with the risk for dementia, Vitaliano says.
Studies have also shown that caregivers often find it difficult to maintain a healthy diet, and it's not uncommon for them to switch to diet of fast and highly processed foods for the sake of convenience.
Caregivers have also been shown to be less physically active than adults the same age who are not taking care of a sick loved one.
Taking Care of Caregivers
With such a complex interplay of physical and emotional factors at work, experts say that the interventions to protect caregivers from dementia need to be just as multifaceted.
"It's too simplistic to think that by telling someone to take care of themselves, they're going to do that," Eskenasi says. "In part because there are too many barriers involved."
The first problem, she says, is that many caregivers don't recognize themselves in that role.
"If your spouse has dementia, you don't say 'I'm a caregiver.' You say, 'I'm a wife,' or 'I'm a partner," she says.
But it's important for people to understand the unique demands of what they're doing so they can take time to protect themselves.
Vitaliano says one thing that has been shown to have significant impact on cognitive decline is exercise. Studies have found that moderate intensity aerobic exercise performed in midlife or later appears to reduce the risk of cognitive decline. For those who are already showing signs of dementia, one study found that a six-month program of high-intensity aerobic activity improved cognitive function.
"It's pretty demanding, in terms of the amount of physical activity that you have to do," he says, but it seems to help.
The other thing he recommends to his patients who are caregivers is taking time for "uplifts" or pleasant events, like golf, gardening, and movies. He recommends that caregivers stop and think about hobbies or friends that they may not have seen in a while and actually set aside time for them in a planned schedule.
"This pleasant event schedule makes tremendous common sense," Vitaliano says, "And it's the kind of stuff my grandmother would have said 'you needed to get a PhD to know that?' But it's incredible how people lose what's right in front of their face when they're facing adversity."
Other kinds of support need to come from the government and community, experts say, given that 14.9 million adults in the U. S. now take care of a loved one with Alzheimer's disease or dementia.
Doctors can help, Eskenazi says, just by taken a moment to switch focus.
"Caregiver health is hidden, and it really is because a doctor never asks, 'How are you?'" she says.