Loneliness in people older than 50 greatly increases their risk of high blood pressure, researchers say in the latest study to underscore the health advantages of friends and family.

The loneliest people studied had blood pressure readings as much as 30 points higher than those who weren't lonely, suggesting that loneliness can be as bad for the heart as being overweight or inactive, the researchers said.

"The magnitude of this association is quite stunning," said University of Chicago scientist Louise Hawkley, the study's lead author.

With earlier research suggesting that more than 11 million Americans older than 50 often feel isolated, left out or lacking companionship, the study could have substantial public health implications if it can be shown that reducing loneliness can lower people's blood pressure, said Richard Suzman, director of a behavioral research program at the National Institute on Aging, which helped fund the study.

Hawkley said the findings hint that one strategy for treating high blood pressure might be to get more involved, "do volunteer work, make yourself useful."

The study of 229 Chicago-area men and women ages 50 to 68 appeared in the March issue of the journal Psychology and Aging.

The results build on earlier research by co-author John Cacioppo, who found that in younger adults loneliness was linked with blood vessel problems that could lead to high blood pressure.

Last year, Harvard research linked loneliness in men with increased blood levels of inflammatory markers associated with heart disease. And a Duke University study found an increased risk of death in socially isolated patients with heart disease.

The research "says something about the importance of social connection in our everyday lives," said Cacioppo, a psychology professor who works with Hawkley at the university's cognitive and social neuroscience center. "Part of living a healthy life is paying attention to friends and family."