A perennial grump? Always see the glass as half empty instead of half full? Might want to brighten up a bit – if, that is, you'd like to live longer. A new study says that the optimists among us may have a lower risk of heart disease and early death.

Researchers led by Hilary Tindle, an internist at the University of Pittsburgh Medical Center, analyzed eight years of data on 97,253 women, age 50 and over, participating in the Women's Health Initiative, a 15-year study launched in 1991 by the National Institutes of Health (NIH). Their findings, released this week at a conference of the American Psychosomatic Society in Chicago: the women who were most cheery were 30 percent less likely to die of heart disease and 14 percent less likely than their pessimistic peers to die from all causes during the study period. The results were even more striking among black women; the optimists among them were 38 percent less likely to die of heart disease and 33 percent less likely to die from all causes.

The researchers caution that their findings only show a link, not a cause-and-effect relationship, between optimism and health outcomes. So what is it about Pollyannas that may make them live longer? It could be that optimistic people tend to be healthier in general; they are more likely to be slim and physically active and less likely to smoke, Tindle says.

"Optimistic people seem to seek medical advice and follow it," she  says, citing research showing that optimists are inclined to stick with diet programs prescribed by their docs. "They [also] have good social networks and strong social relationships," which could help them cope with chronic stress, a risk factor for heart disease.

So are pessimists doomed to die early? Not necessarily, Tindle says. This is just one study, and more research is needed to get to the bottom of that question.