Researchers say older adults who have children and grandchildren tend to live longer than people who don’t have children … for a number of reasons.

Parents know that those little bundles of joy bring them plenty of fun and satisfaction.

Now it turns out having children has an unanticipated benefit: longer life.

According to a new study out of Sweden, older parents live longer than their neighbors who don’t have children.

Parenthood is associated with a longer life, particularly in older age, when health and abilities may have declined, according to research published in the Journal of Epidemiology & Community Health.

The difference is apparent by age 60, the researchers say, and may be as much as two years.

The gender of the child or children does not seem to matter.

For instance, the one-year risk of death for an 80-year-old man with a child was 7.4 percent, compared with 8.3 percent for a man of the same age who didn’t have a child.

To investigate whether parenthood might prolong life in older adults, the researchers tracked the lifespan of 704,481 men and 725,290 women from the age of 60 and on. The participants, who all lived in Sweden, had been born between 1911 and 1925.

The study concluded at the end of 2014, as the researchers also gathered registry data on the participants’ marital status and the number and sex of any children they had.

Read more: ‘Baby boxes’ and new parents »

The researchers’ findings come as no surprise to Donna Butts, executive director of Generations United, an organization based in Washington, D.C., that promotes three-generation solutions to personal and societal problems.

She has a solution for those older adults missing out on the benefits of children.

“If you don’t have a child in your life, find one,” she said.

There is no evidence that becoming a surrogate grandparent at age 60 comes with a longevity benefit, but Butts sees it as positive all around.

“Everyone needs some purpose,” Butts said. “Intergenerational activities are positive on all fronts.”

“It makes sense,” she said. “Research shows how much good comes from older adults being with young people.”

For one thing, the older people reported having a greater social network.

“They are more engaged, have more reason to get up in the morning,” she said.

One of the easiest ways to interact with a child, according to Butts, is through reading. Many literacy programs count on older volunteers reading to children who need to hear stories or improve their reading skills or even share quiet time.

“Sometimes you just need to listen to a child,” she said.

An article in the March issue of the AARP Bulletin lists 50 ways to live longer, and one of them is to take care of grandchildren.

The Swedish research team also found a similar link between longevity and providing care to grandchildren.

Read more: Study finds grandparents are essential for human evolution »

The newest data suggest you don’t even need to wait for a grandchild or babysit the ones who’ve arrived.

You get the bonus by the mere fact of having procreated.

Lead author on the study is Karin Modig, PhD, who teaches epidemiology at the Institute of Environmental Medicine, Karolinska Institutet, in Stockholm.

The research protocol required taking account of influential factors, such as educational attainment.

It turned out the risk of death was lower among those who had had at least one child than those who did not have a child — and more so among men than among women.

Researchers said the lower risks were evident among those who were married and unmarried, but seemed to be stronger among those who weren’t married, at least among the men.

The difference in death risk was 1.2 percent among unmarried men and 0.6 percent among those who were married.

Unmarried men might be relying more heavily on their children in the absence of a partner, the researchers suggest. They are also likely to be less educated, whereas the opposite tends to be true of women.

The research team wondered if the child’s gender would be significant as suggested by a previous study. Perhaps that research had focused on the traditional social benefits of having a daughter. Other types of support, including advocacy and navigating the health system, could be provided by sons as well, they said.

The team concluded, “Our finding that the association grew stronger when parents became older is further in agreement with research suggesting that childless people face support deficits only toward the end of life.”

In fact, that two factors (having a child and longevity) coexist does not prove a causal relationship between them.

In the meantime, until further evidence is revealed, speculation about what this finding means continues both inside and outside the scientific community.

Read more: Nature vs. nurture: How much influence do parents have? »