Gail Schwartz wants to keep her 85-year-old husband out of a nursing home as long as she can, but it isn’t easy.

Because David Schwartz, a retired lawyer, has vascular dementia and can no longer stay alone in their home in Chevy Chase, Md., she tends to his needs from 1 p.m. to 11 p.m. Monday through Saturday and all of Sunday.

An aide now stays overnight because Schwartz awakened so frequently, disoriented and upset, that his wife began to suffer the ill effects of disrupted sleep. “I need my rest,” she said. “I’m no spring chicken myself.”

Indeed, Gail Schwartz is 78. While she thinks her husband does better at home — “he’s getting 24-hour attention, and you don’t get that in a nursing home,” she said — friends point out that the arrangement is much harder on her. She worries, too, about costs climbing as Schwartz’s health declines and his needs increase.

For now, though, she manages, part of an apparently growing phenomenon: The old taking care of the old.

Every few years, the National Alliance for Caregiving and the AARP Public Policy Institute survey the state of caregiving; their latest report focused in part on caregivers older than 75. They constitute 7 percent of those who provide unpaid care to a relative or friend, the survey found — more than 3 million seniors helping with the activities of daily living (bathing, dressing, using a toilet), instrumental activities of daily living (shopping, transportation, dealing with the health care system) and a rising tide of medical and nursing tasks.

Almost half of them report caring for a spouse; the others assist siblings and other relatives, friends or neighbors, most also 75 or older. About 8 percent of these oldest caregivers still care for parents.

The aging of the population has thrust more seniors into this role, said Gail Hunt, president and chief executive of the National Alliance for Caregiving. “There didn’t use to be so many 95-year-olds,” she said, “and someone’s caring for those 95-year-olds.”

People older than 75 spend an average of 34 hours a week on caregiving tasks, the National Alliance for Caregiving report found, 10 hours more than caregivers overall. The typical older caregiver in the study had been providing care for more than five years.

There is no great mystery about the kinds of policies and programs that could better sustain caregivers. Hunt rattled off several, including regular respite care, home aides covered by Medicare, tax credits for family caregivers and more subsidized adult day programs.

Yet people like Alvin Vissers, 75, still shoulder the role. He retired from his job as a construction project manager near Brevard, N.C. two years ago to help his wife, Ronda, 75, who is in the later stages of Alzheimer’s disease. Ronda Vissers, a nurse, can no longer speak much and needs help with nearly everything — bathing, dressing, eating. Without constant monitoring, she may wander outside.

“I told her when this started, ‘Sweetheart, you’ve cared for me for 50 years; I guess it’s my turn,’ ” he recalled. “Now, I’m finding out what those words mean.”