Want to live longer? Researchers are offering a simple prescription to help you do that: spend less time alone.

Loneliness and social isolation are risk factors contributing to early mortality for all ages, they suggest, and social connections are an important health and lifestyle factor.

A data analysis suggests the association between loneliness and risk for early mortality is actually greater in young populations than among older populations, the researchers from Brigham Young University report in the journal Perspectives on Psychological Science.

Social isolation and loneliness better predicted premature death among populations aged less than 65 years, they said, despite older people being more likely to be lonely and experiencing a higher mortality risk overall.

"Not only are we at the highest recorded rate of living alone across the entire century, but we're at the highest recorded rates ever on the planet," says study co-author Tim Smith. "With loneliness on the rise, we are predicting a possible loneliness epidemic in the future."

Loneliness and social isolation sound similar but can take different forms, the researchers point out; someone may be surrounded by many people but still feel alone, while other people may isolate themselves out of a preference for being alone.

However, the effect on mortality is much the same in either case, the researchers suggest.

Previous research by Smith and study lead author Julianne Holt-Lunstad had put the heightened risk of mortality from loneliness in the same category as being an alcoholic or as smoking 15 cigarettes a day, and the new study shows it to be even more of a risk factor than obesity.

"The effect of this is comparable to obesity, something that public health takes very seriously," says Holt-Lunstad. "We need to start taking our social relationships more seriously."

The researchers conducted a meta-analysis of a number of health studies conducted between 1980 and 2014, with a total of more than 3 million participants surveyed about loneliness, social isolation and living alone.

A lack of social connections presents an added mortality risk, while the existence of relationships provides a positive health effect, regardless of socioeconomic status, gender, age or pre-existing health conditions, they found.

"In essence, the study is saying the more positive psychology we have in our world, the better we're able to function not just emotionally but physically," Smith says.