https://news.harvard.edu/gazette/story/2017/04/over-nearly-8...
“[F]ollowed 724 men since they were teenagers in 1938. (Approximately 60 men, now in their 90s, are still left.) The group consisted of men from various economic and social backgrounds, from Boston’s poorest neighborhoods to Harvard undergrads. (President John F. Kennedy was even part of the original group.) Over the years, the researchers have collected all kinds of health information, and every two years they ask members questions about their lives and their mental and emotional wellness. They even interview family members.”
“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 discontents, help to delay mental and physical decline, and are better predictors of long and happy lives than social class, IQ, or even genes. That finding proved true across the board among both the Harvard men and the inner-city participants.”
“When we gathered together everything we knew about them about 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 the most satisfied in their relationships at age 50 were the healthiest at age 80.”