The world's longest study on human happiness reveals that relationship quality at midlife predicts health decades later better than cholesterol levels
The secret to living past 90 may have nothing to do with your gym membership or your vegetable intake. According to the Harvard Study of Adult Development, the longest-running scientific study on human happiness and longevity, the most consistent predictor of a long, healthy life is something far simpler: strong relationships.
"Good relationships keep us happier and healthier," according to Dr. Robert Waldinger, director of the 85-year study and professor of psychiatry at Harvard Medical School. "People who are more socially connected to family, to friends, to community, are happier, healthier, and live longer."
What 85 years of research reveals
The Harvard Study began in 1938, tracking 724 participants from adolescence into old age. Researchers collected thousands of data points, from brain scans to blood work, questionnaires to in-depth interviews. The study has since expanded to include spouses and more than 1,300 descendants of the original participants.
The findings consistently point to one conclusion: relationship satisfaction matters more than genetics, wealth, fame, or IQ when it comes to predicting who will thrive in old age. In fact, researchers found in findings published by the Harvard Gazette that people's level of satisfaction with their relationships at age 50 was a better predictor of physical health at 80 than their cholesterol levels were.
"The role of genetics and long-lived ancestors proved less important to longevity than the level of satisfaction with relationships in midlife," the Harvard Gazette reported.
Loneliness rivals smoking as a health risk
The flip side of connection is equally striking. Waldinger has been direct about the health consequences of isolation: "Loneliness kills. It's as powerful as smoking or alcoholism."
Research supports this stark assessment. One study examining data from more than 309,000 people found that lack of strong relationships increased the risk of premature death from all causes by 50%, according to a Harvard Health analysis. That effect on mortality risk is roughly comparable to smoking up to 15 cigarettes a day and greater than the risks posed by obesity and physical inactivity.
The Centers for Disease Control and Prevention reports that one in four adults aged 65 and older is considered socially isolated. Loneliness has been associated with a 50% increased risk of dementia, 29% increased risk of heart disease, and 32% increased risk of stroke.
How relationships protect the body
Participants with robust social connections showed lower rates of diabetes, arthritis, cognitive decline, and other chronic conditions. Researchers believe close relationships function as stress regulators, helping the body return to equilibrium after challenging events.
"Those good relationships don't have to be smooth all the time," Waldinger noted in his TED Talk, which has been viewed more than 42 million times. "Some of our octogenarian couples could bicker with each other day in and day out, but as long as they felt that they could really count on the other when the going got tough, those arguments didn't take a toll on their memories."
The research found that women who felt securely attached to their partners were less depressed, more satisfied in their relationships, and showed better memory function years later compared to those experiencing frequent marital conflict.
It's never too late to build connections
The Harvard Study also debunked the notion that personalities become fixed by age 30. Researchers observed participants who struggled in their twenties become thriving octogenarians, while others who started as "stars" declined due to factors like alcoholism or untreated depression.
The study's findings extend beyond romantic partnerships. The benefits of connection include friendships, workplace bonds, community involvement, and even brief daily interactions. Dr. Waldinger and co-author Dr. Marc Schulz emphasize in their book "The Good Life" that small, consistent efforts to invest in relationships compound over time.
"Taking care of your body is important, but tending to your relationships is a form of self-care, too," Waldinger has said in media interviews. "That, I think, is the revelation."
What's next
The Harvard Study continues to follow participants and their descendants, with researchers now examining the children of the original subjects who have reached late middle age. As the U.S. Surgeon General has declared loneliness a public health epidemic, these findings take on new urgency.
For those hoping to live longer, the prescription may be surprisingly straightforward: call an old friend, join a community group, or simply give someone your undivided attention. The science suggests it could add years to your life.
