A rare study that tracked the lives of 724 men for nearly 80 years revealed the most powerful indicator of success and happiness doesn’t lie in our genes, wealth, social class, or IQ. The Harvard Study of Adult Development, the longest study of adult behavior, found that strong social connections made people happier and physically healthier.

According to Inc.com, beginning in 1938, researchers divided the men into two groups for the study. The first group were sophomores at Harvard. The second was a group of boys of similar age from Boston’s poorest neighborhoods. For the next 79 years they asked the participants about their work, their lives, and their health. The results showed that flourishing in life is linked to having close ties with family, friends, and community.

One of the study authors, Robert Waldinger, is publishing the data in a new book scheduled for release in January 2023, called The Good Life. Of the original cohort recruited for this lengthy study only a handful are still alive, says The Harvard Gazette. Among the original recruits were eventual President John F. Kennedy and longtime Washington Post editor Ben Bradlee. Women weren’t included in the original research because Harvard didn’t allow female students at the time.

“The surprising finding is that our relationships and how happy we are in our relationships has a powerful influence on our health,” noted Waldinger, director of the study, and a psychiatrist at Massachusetts General Hospital. “Taking care of your body is important but tending to your relationships is a form of self-care, too. That, I think, is the revelation.”

Close relationships, more than money or fame, are what keep people happy throughout their lives, the study revealed. Those ties protect people from life’s ups and downs and tend to delay both mental and physical decline. They are better predictors of long and happy lives than social class, IQ, or even genes. That finding proved true across the board, from the Harvard men and the inner-city participants.

“When we gathered together everything we knew about them at age 50, it wasn’t their middle age cholesterol levels that predicted how they were going to grow old,” said Waldinger in a popular TED talk. “It was how satisfied they were in their relationships. The people who were most satisfied at age 50 were the healthiest at age 80.”

On the other hand, Waldinger also observed that “people who were more isolated than they want to be from others find they are less happy, their health declines in midlife, their brain function declines sooner and they live shorter lives than people who are not lonely,” according to Inc.com.

“The sad fact is that at any give time, more than one in five Americans will report that they’re lonely,” said Waldinger. He added that instead of focusing on the quantity of friendships, it is important to focus on the quality.

The study found that conflict adversely affects our health so, for example, a bad marriage is less healthy than getting a divorce. And having a warm, wholehearted relationship is protective.

“The good life,” Waldinger concluded, “is built with good relationships.”