Lynne Ingersoll and her cat, Jesse, spent a quiet Thanksgiving Day together in her small bungalow in Blue Island, Ill.

A retired librarian, Ingersoll never married or had children. At 77, she has outlived her parents, three partners, her two closest friends, five dogs and eight cats.

When her sister died three years ago, Ingersoll joined the ranks of older Americans considered “kinless”: without partners or spouses, children or siblings. COVID-19 largely suspended her occasional get-togethers with friends, too. Now, she said, “my social life consists of doctors and store clerks — that’s a joke, but it’s pretty much true.”

Like many older adults, Ingersoll copes with an array of health problems: kidney disease, asthma, heart disease requiring a pacemaker, arthritis that makes walking difficult even with a cane. She’s managing, but “I can see a time when that’s not going to be true,” she said. “I’m not sure what I’m going to do about it.”

An estimated 6.6% of American adults 55 and older have no living spouse or biological children, according to a study published in 2017 in The Journals of Gerontology: Series B. (Researchers often use this definition of kinlessness because spouses and children are the relatives most apt to serve as family caregivers.)

About 1% fit a narrower definition: lacking a spouse or partner, children and biological siblings. The figure rises to 3% among women over 75.

Those aren’t high proportions, but they amount to a lot of kinless people: close to 1 million older Americans without a spouse or partner, children or siblings in 2019, including about 370,000 women over 75.

“We assume that everyone has at least some family, but that’s not the case anymore,” said Rachel Margolis, a sociologist at the University of Western Ontario and co-author of the study.

Several demographic factors have fostered increased kinlessness. Baby boomers have lower marriage rates and higher divorce rates than their parents, and more have remained childless. The rise of so-called gray divorce, after age 50, also means fewer married seniors, and extended life spans can make for more years without surviving family.

“All the pathways to singlehood have grown,” said Deborah Carr, a sociologist and researcher at Boston University.

Among older couples, cohabitation has increased as an alternative to marriage, but those seniors are less likely than married couples to receive care from their partners. Those in committed relationships who don’t live with their partners are less likely still.

In addition, seniors who are Black, female and have lower levels of wealth have particularly high rates of kinlessness.

The growing number of kinless seniors, who sometimes call themselves “elder orphans” or “solo agers,” worries researchers and advocates because this group faces numerous disadvantages.

A study of middle-aged and older adults in Canada found that those without partners or children (this study included no data on siblings) had higher levels of loneliness. They were less likely to participate in activities like sports, cultural or religious groups, or service clubs — a predictor of later cognitive impairment.

Kinless Americans die earlier. Margolis and her co-authors, using data from the Health and Retirement Study, found that a decade after respondents’ initial interviews, more than 80% of seniors with partners and children had survived, compared with only about 60% of those without either.

At the end of life, researchers at Mount Sinai in New York reported, people without partners and children had received fewer hours of caregiving each week and were more likely to have died in nursing homes.

“Getting old is hard under the best of circumstances and even harder if you’re going it alone or with weak social ties,” Carr said.

On the other hand, meet Joan DelFattore, 76, a retired English professor at the University of Delaware. Like some solo agers, “I had a sense from an early age that I simply didn’t see myself as a wife and mother.” Preferring to live alone, “I went about constructing a single life.”

DelFattore, who is in good health, still writes and researches, and she teaches a graduate course every other fall. She stays in near-daily contact with a group of friends, walking several times a week with one of them, and remains close to cousins in New Jersey, with whom she spent Thanksgiving. She takes an active role in several local organizations.

And she dislikes “the cultural perception that old people being without immediate family has to mean that you’re needy, you don’t have support.”

Sociologists call that strategy “substitution” — turning to friends and neighbors for the connections and sustenance that families traditionally have provided.

In Mount Lebanon, Pa., for instance, Celeste Seeman, who is divorced and childless and has lived alone for 25 years, has befriended neighbors in her apartment building. When one had surgery recently, Seeman, 65 and still working as an embroidery machine operator, walked the neighbor’s Chihuahuas, did her laundry and called her almost daily for weeks.

“I hope that what goes around comes around,” Seeman said.

Because she has outlived her family, after caring for her parents until their deaths, there’s no remaining relative to provide similar help if she needs it herself.

A study of sole family survivors, the last members of the families they grew up in, found that, for unclear reasons, they were disproportionately likely to lack spouses or partners and children, and thus were doubly vulnerable.

Of course, having family is no guarantee of help as people age. Still, “our system of caring for the aged has functioned, for better or worse, on the backs of spouses and, secondarily, adult children,” said Susan Brown, a sociologist at Bowling Green State University and an author of the study of sole family survivors.

Relying on substitutes has limitations. About two-thirds of older Americans will eventually hit a rubber-meets-the-road moment and require help with the activities of daily living, such as bathing, dressing and using the toilet.

DelFattore has prepared for that possibility by buying insurance for long-term care years ago, so that she can hire home care aides or afford assisted living. Few Americans have done that or can afford the costs, yet most will also be unable to pay for sufficient care out of pocket and don’t have incomes low enough to qualify for Medicaid.

“Policies tend to lag behind reality,” Carr said. “There was the belief in past decades that older adults would be married and have children; that’s what the classic American family looked like. It no longer does.”

In the absence of any broad public program, experts suggest a variety of smaller solutions to support kinless seniors.

Shared housing and co-housing, providing safety and assistance in numbers and community, could grow, especially with public and philanthropic support. The village movement, which helps seniors age in place, might expand as well.

Revised family-leave policies and caregiver-support programs could include friends and neighbors, or more distant relatives like nieces and nephews.

However governments, community organizations and health care systems begin to address the issue, there’s little time to waste. Projections indicate that kinlessness will increase greatly as the population following the baby boom ages.

“Younger people are less likely to marry and have children, and they have fewer siblings” as family sizes shrink, Brown said. “How will they navigate health declines? We don’t have a good answer. I’m not sure people are paying attention.”