Could there be measurable benefits to your health, and to your brain in particular, from being a caregiver?

It’s practically become an article of faith that the reverse is true, that caring for an elderly relative is so stressful, relentless and draining that it takes a toll on your well-being. Some studies have shown that it can increase your risk of depression and heart disease, impair your immune system, even contribute to death.

That caregiving could actually provide some health advantage is so counterintuitive that when Lisa Fredman, a Boston University epidemiologist, first saw such results emerging from her study of elderly women, “I thought, what on earth is going on here?” she recalled. “I blamed myself. I thought something was wrong with my data.”

But over several years of studying the differences between caregivers and non-caregivers in four locations (Baltimore, Pittsburgh, Minneapolis and Portland, Ore.), Dr. Fredman and her colleagues found that while caregivers were indeed more stressed, they still had lower mortality rates than non-caregivers over eight years of follow-up.

In another study of about 900 women drawn from the same four-site sample, even those classified as high-intensity caregivers — because they performed more functions for their dependent relatives — maintained stronger physical performance than non-caregivers. On tests like walking pace, grip strength and the speed with which they could rise from a chair, the high-intensity group declined less than lower-intensity caregivers or non-caregivers over two years.

“That was a shocker,” Dr. Fredman said.

Now Dr. Fredman and her co-author Rosanna Bertrand, a health policy associate at Abt Associates in Cambridge, Mass., have gone back to this pool of women to look at their cognitive functioning. Here, again, caregivers did significantly better on memory tests than did non-caregivers followed over two years. Though the groups were about the same average age, in their early to mid-80s, caregivers scored at the level of people who were 10 years younger.

Along with what’s called “caregiver burden,” gerontologists and psychologists use the phrase “caregiver gain” to reflect the fact that this role, which often exacts such high costs, can bring rewards. But they’ve typically described those rewards in psychological, emotional and even spiritual terms: growing confidence in one’s abilities, feelings of personal satisfaction, increased family closeness. That caregivers can walk faster or recall more words on a memory test — that’s news.

Dr. Fredman has begun referring to this notion that caregivers are not invariably beaten down by their responsibilities as the “healthy caregiver hypothesis.” Taken together, her studies provide some evidence that caregivers, however stressed, may be stronger and stay stronger than women of the same ages who don’t undertake those tasks. The interesting question is why.

You can’t randomize studies like this, assigning some old women to serve as caregivers but not others. So it’s likely that a big part of the differences, Dr. Fredman said, stemmed from self-selection: Women become caregivers because they are healthy enough to shoulder that responsibility. “If you’re not healthy,” she said, “it goes to your daughter or daughter-in-law.” It’s not surprising, therefore, that even high-intensity caregivers have and maintain more physical strength.

It’s also true that Dr. Fredman’s definition of a caregiver sets a fairly low bar, including anyone who performs even one “instrumental activity of daily living,” such as helping someone with bill-paying or phone use. Hands-on help with bathing or toilet use is clearly more stressful, physically and emotionally; caring for someone with dementia can be particularly arduous.

But caregiving itself may provide real benefits. “Most caregiving activities require you to move around a lot,” Dr. Fredman pointed out. “It keeps people on their feet, up and going.” And exercise is known to improve physical health and cognition.

Moreover, Dr. Bertrand added: “Caregiving often requires complex thought. Caregivers monitor medications, they juggle schedules, they may take over financial responsibilities.” That, too, can ward off cognitive decline.

Plus there’s the whole matter of people benefiting from having a purpose. It’s hard to quantify, but it’s real.

So it’s fair to say that the question of how caregiving impacts the caregiver is more complicated and individual than we think. Both could be true, the burdens and the benefits, depending on how demanding the job is and a host of other factors.

That caregiving is a very tough job is beyond debate. “We don’t want to overstate this and say it’s good for caregivers and have governors across the country rush to cut support programs that help families,” said Steven Zarit, a Penn State gerontologist who has studied caregiving. (Of course, governors seem all too eager to do that anyway.)

Still, “it may not be as predictive of their demise as previously thought,” Dr. Bertrand said of elder care and caregivers. “There are potentially some positive aspects.”

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