The morning's activities were in full swing at the Sutter SeniorCare program in Sacramento, Calif., and the adult day health clients had gathered in the dining room for coffee.

Loretha Loggins, a vivacious longtime volunteer, made her way from table to table, chatting.

"I love the little seniors," said Loggins, a retired nursing assistant. "We laugh and have a good time."

She's 83, and many of the center's clients are younger by a decade. Or two.

While experts have long worried that taking care of others can exact a steep physical toll on older adults, especially spouses caring for people with dementia, new Boston University research shows that less-intense caregiving duties can improve both physical and cognitive function in the elderly.

Helping other seniors, in short, can keep people like Loggins energetic and young.

And recent studies have shown that many older adults prefer that the people who assist them be older as well.

"People like a more mature caregiver because of that shared life experience," said Dan Wieberg, a spokesman for Home Instead Senior Care, whose 65,000 home-care workers across the country include more than 26,000 who are 60 and older.

"They can relate."

As the population ages, the number of older caregivers is on the rise.

The Sloan Center for Aging and Work estimates that women age 55 and older will account for 30 percent of the home-care workforce by 2018, up from 22 percent in 2008.

That same age group represents almost 51 percent of the nation's volunteer force, according to the Bureau of Labor Statistics.

Even so, it's hard to track which of them are seniors helping fellow seniors. Harder still is quantifying the contributions of informal volunteers who don't consider giving an older neighbor a drive to the grocery store or making soup for an elderly church member to be volunteer work at all.

Nancy Freeman, a registered nurse who works with Eskaton's Live Well at Home telephone reassurance program, likes to check on some of her phone clients in person once she's off the clock.

"I enjoy going out and seeing them," said Freeman, 74. "If I've made a connection, I see what I can do for them as a friend."

Her own life experiences as a breast-cancer survivor and macular-degeneration patient have given her common ground with many of her clients, most of whom are 60 and older.

"When somebody has cancer, I can talk to them," she said. "When I notice a note that a person has macular degeneration, I handle the call myself. That extra spark of connection counts."

Her clients assume she's younger than they are.

"They're surprised," she said. "They say, 'You wouldn't understand that.' Yes, I would."

That shared sense of experience makes all the difference to Sutter SeniorCare participants, said activities supervisor Kathy Harrison.

"Our clients have a peer in the volunteer," she said. "They're dealing with a lot of the same problems."

Her volunteers, like Loggins, come from Sacramento County's Senior Companion program, which supplies older volunteers to a variety of home- and community-based programs for fellow seniors.

"They recognize the same music and entertainers," said the program director, Mark Snaer. "They recognize the same key events."

And they're likely dealing with the same life events: widowhood, for example, and the loss of lifelong friends, as well as the growing need to rely on their grown kids.

"It's like the parents become the children and the children become the parents," Loggins said to Yvonne Friel, 62, a SeniorCare client.

Friel nodded, happy to spend time with Loggins.

"She's just wonderful," Friel said. "We have coffee together and talk."