Living to a ripe old age takes some effort, and adhering to a healthy lifestyle might top the list. After all, rare are the octogenarians with a three-pack a day cigarette habit. Also, exercise helps, as does a balanced diet. And if your mom and dad’s 80th birthdays were celebrated at parties where your grandparents brought gifts, guess what? You might have good genes.

Scientists say something else might help you attain great longevity. Hint: You won’t find it at the bottom of a half-empty glass.

It’s optimism.

A study by Massachusetts researchers involving more than 70,000 people found that the most optimistic in the bunch had, on average, 11% to 15% longer lifespans. Those glass-half-full folks also had an up to 70% chance of reaching 85 years in age than gloomier sorts.

Participants were quizzed about their health and their outlook on life, and then tracked for either 10 or 30 years. Findings were adjusted for other factors affecting age, including education, depression and primary care visits.

The work reached no conclusion on why an optimistic outlook helps us live longer. But previous research points to the idea that cheerier people are able to better bounce back from life’s inevitable hardships. And scientists have linked stress to physical problems including heart disease.

The study’s authors also note that it’s possible optimists have healthier habits, like regular exercise or an avoidance of smoking.

And pessimists, take heart. Psychologists say a grim outlook on life isn’t like having big ears or a receding chin. Optimism, they note, can be taught. Just be open to it. You might find you have a lot to look forward to.