The mortality impact of being socially disconnected is like smoking up to 15 cigarettes a day, the U.S. Surgeon General said in a 2023 report on the nation’s loneliness “epidemic.”

Stressors “break down our bodies in all kinds of ways,” said David Sbarra, a psychology professor and director of the Laboratory for Social Connectedness and Health at the University of Arizona.

People also often try to regulate the negative effects of stress via drinking, smoking or doing drugs, which are other pathways to adverse health impacts, Sbarra said.

By contrast, having broader social networks and more social activity delays and slows cognitive decline, for example, Waldinger said. The Harvard study found that married people also lived longer than their single counterparts — five to 12 years longer for women and seven to 17 years longer for men, on average.

The transition into retirement “is a period of stress,” Sbarra said.

For one, there’s an “upheaval” associated with identity transition. Retirees close one chapter of their lives and must choose the contours of their next chapter, he said.

That stress can become chronic if people don’t manage the transition well, and physical health may suffer as a result, he added.

Relationships and the quality of those connections “play a key role” in helping regulate stress, Sbarra said. However, the bulk of many people’s close relationship needs may be met at work, he said. In such cases, retirement strips away those interactions.

“Some people say, ‘It’s too late for me’” to make new social connections, Waldinger said.

“One of the things we know from study: It isn’t too late. People make all kinds of new connections and friendships when they’re older, in all phases of life,” he added.

Experts say finances do have a bearing on happiness in retirement, to a point.

“You need to have your [financial needs] met,” Waldinger said.

Just as the lack of strong social connections is a cause of stress, so is the lack, or perceived lack, of financial resources, said Yochai Shavit, director of research at the Stanford University Center on Longevity.

However, if the goal of retirement is to live a happy, healthy and fulfilling life, social capital is as important as financial capital, he said.

“We are very strategic when it comes to our money and planning for retirement, and perhaps not strategic in the same way … when it comes to planning our social and emotional capital,” Shavit said.

The Harvard study shows it’s not just the quantity of social connections that’s important; it’s the quality of your close relationships that matters, Waldinger said.

For example, living amid conflict is “really bad” for our health, he said in his TED Talk. A “high-conflict” marriage without much affection is perhaps worse for health than getting a divorce, for example, he said.

Further, loneliness is a subjective experience, he told CNBC. Some people are introverts who may only need one or two meaningful relationships, for example.

“You can be lonely and have a ton of people around you, or not be lonely and be a hermit on a mountain,” he said.

Near-retirees or retirees who want to assess the quality of their relationships and/or strengthen their existing connections can take three steps, Waldinger said.

First, ask: Do I have enough people I feel connected to in my life? Am I connected to others in the way I want to be?

“It’s really [about] checking in with yourself,” Waldinger said.

Second, assess whether you can improve relationships with the people already in your life whom you value and enjoy spending time with. Can you do more with what you already have?

This could be anyone: perhaps a sibling, friends or romantic partner. For example, you could replace screen time with people time, liven up a relationship by doing something new together, such as long walks or date nights, reach out to a family member you haven’t spoken to in years. Even talking to someone on the phone, or sending a text or e-mail, can help.

“It doesn’t have to be heavy lifting,” Waldinger said.

Third, assess whether you can form new connections.

Among the easiest and quickest ways to do this is by doing something you enjoy or care about alongside people you don’t know yet, Waldinger said.

For example, join a gardening club, political campaign, church group or a campaign to prevent climate change, he said.

It becomes easier to start conversations with new people because you have this thing in common, he added.

The people in the Harvard study who were happiest in retirement were the ones who actively worked “to replace workmates with new playmates,” Waldinger said in his TED Talk.

“Relationships are messy and they’re complicated, and the hard work of tending to family and friends, it’s not sexy or glamorous,” he said during that TED Talk. “It’s also lifelong. It never ends.”