This is part of a regular series on aging well.

If you're feeling a little long in the tooth, join the club. Curling, pottery, wine appreciation, bridge – any club will do. The trick is to socialize in groups, which a spate of new studies suggests is a leading way to live long and prosper.

In fact, belonging to social groups is as effective as exercise in preventing death in early retirement, according to a study published in February in the journal BMJ Open.

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Researchers looked at the social habits of 424 Britons as they transitioned into retirement. Here's what they found:

Some retirees may have withdrawn from group activities because of health issues that hastened their demise. But over all, physical health was not a significant predictor of death when other variables, such as age, sex, socioeconomic status and group memberships, were factored in, the study said.

Being part of social groups boosts self-esteem, resilience and mental health and may encourage healthy habits, researchers say.

Joining religious, volunteer or community groups may even improve sleep – another factor in age-related decline, according to a study published early this month in the Journal of Social Science and Medicine. Researchers analyzed the link between older adults' social group activities over five years and their sleep, using self-reports of sleep habits and a device called an actigraph, which measures sleep quality.

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The result: "People who are more active in social activities sleep better," said Dr. Jen-Hao Chen, an assistant professor of health sciences at the University of Missouri. While it's possible that people who sleep better simply have more energy to socialize in the first place, participation in group activities may in itself reduce stress and promote good sleep, Chen said.

He added that early retirement is a time of flux. More than two-thirds of the people in the study changed their level of group participation over the five-year period. Some may have withdrawn from social activities to care for grandchildren. Others may have used their extra free time to get more involved in sports, volunteering or community groups.

Chen noted that socializing one-on-one, such as helping a neighbour or friend, does not offer the same health benefits as group activities. The reasons for this are uncertain, he said, but "that kind of relationship may drain older adults' resources, their emotional energy."

For introverts, the focus on group activities may not be good news. But hopefully it's never too late to join a club that would have you as a member.