Harvard followed people for 86 years, one thing kept predicting a longer life

The Harvard Study of Adult Development, one of the world’s longest-running studies on happiness, has followed participants since 1938. After decades of health examinations and interviews, researchers repeatedly arrived at one central conclusion: good relationships are among the strongest predictors of long-term health and happiness.

People who felt satisfied with their friendships and family relationships during middle age were healthier decades later. They also recovered better from illness and experienced fewer chronic diseases. The US Centers for Disease Control and Prevention also notes that social connection supports both mental and physical health, while loneliness and isolation are associated with poorer health outcomes.

Actor Dick Van Dyke, who turned 100 at the end of 2025, has always remained socially active, continuing to perform, interact with people and stay involved in work he genuinely enjoys. He credited his longevity not to diet or exercise, but to a simple outlook: ‘I never wake up in a bad mood.’

Research also suggests that having a strong sense of purpose supports healthy ageing. Researchers studying families of centenarians have found that individuals with a stronger sense of purpose often experience lower rates of disability, disease and cognitive decline.

Image: Wikimedia Commons/by Gage Skidmore