Loneliness counts as a legitimate health risk in people with serious illness, say Danish researchers. In a large new study, investigators from Copenhagen University Hospital found that cardiac patients who reported loneliness were more likely to die within a year of hospital discharge.

Over 13,000 patients completed questionnaires about physical and psychological wellbeing and health behaviors such as smoking, drinking and medication habits. After accounting for these factors, lonely women were nearly three times as likely to have died from any cause after a year as women who didn’t report feeling lonely. Similarly, lonely men were more than twice as likely to have died from any cause. The investigators also found that loneliness was associated with significantly poorer physical health after a year.

It’s not clear whether the illness or the feelings of loneliness come first. But previous research suggests that loneliness is associated with changes in cardiovascular, neuroendocrine and immune function as well as unhealthy lifestyle choices, wrote lead researcher Anne Vinggaard Christensen, Ph.D.

“There are indications that the burden of loneliness and social isolation is growing,” said Christensen. “[I]ncreasing evidence points to their influence on poor health outcomes being equivalent to the risk associated with severe obesity. Public health initiatives should therefore aim at reducing loneliness,” she concluded.