Loneliness in adulthood follows a U-shaped pattern: it’s higher in younger and older adulthood, and lowest during middle adulthood, according to researchers who analyzed nine longitudinal studies from around the world. Their study also identified several risk factors for heightened loneliness across the whole lifespan, including social isolation, sex, education and physical impairment.

The U-shaped pattern was replicated across datasets from studies conducted in various countries, including the UK, Germany, Sweden, the Netherlands, and Australia, among others. Only one dataset was from the US, which coauthor Eileen Graham, associate professor of medical social sciences at Northwestern University Feinberg School of Medicine, Chicago, said points to how widespread the loneliness epidemic is globally.

Individuals with higher persistent loneliness were disproportionately women, more isolated, less educated, had lower income, had more functional limitations, were divorced or widowed, were smokers, or had poorer cognitive, physical or mental health.

While the study didn’t specifically examine why middle-aged adults are the least lonely, Graham said it could be because the many demands on a middle-aged person’s life often involve social interactions, such as being married, going to work and making friends with the parents of children’s friends.

Lacking connection can increase the risk for premature death to levels comparable to smoking daily, according to the office of the US Surgeon General, who called for action to address America's loneliness epidemic. Graham said her findings underscore the need for targeted interventions to reduce social disparities throughout adulthood to hopefully reduce levels of loneliness, especially among older adults.

Perhaps one day general practitioners could assess levels of loneliness during regular wellness visits to help identify those who might be most at risk, she suggested.

To read the abstract of the study, published in Psychological Science, click here