The 1993 movie Grumpy Old Men played up a common stereotype about those who live well beyond their golden years. With lines like, "Do me a favor. Put your lip over your head... and swallow," they're not the nicest lot. But a study published in the May 2012 issue of Aging found that those who lived to be 100 generally had a "positive attitude towards life and emotional expression." It also found that those positive traits are located in your genes.

But the study is a long way from proving that a positive outlook causes these centenarians to live longer, said Dr. Nir Barzilai, one of the study's researchers. "There are personality changes and physiological changes that make a lot of elderly people become just more agreeable personalities," Barzilai said. "It has nothing to do with what got them to be 100."

Researchers looked at a group of more than 500 Ashkenazi Jews age 95 to 107, and 700 of their offspring. They're a favorite in longevity studies because they're genetically homogenous (40 percent of Ashkenazim derive from just four Jewish mothers). By creating a personality trait index focusing on levels of neuroticism, positive attitudes toward life and emotional expression, researchers found that the group was less likely to have high levels of neuroticism and were more likely to be extroverts. The same was true of their children, creating an argument for personality genes.

"My own interpretation from the study is that, yes, this is the personality we’re seeing [but] we still have to figure out if it’s important," Barzilai said. "The most interesting thing for me is to see if the longevity genes influence the personality."

Yet the health benefits of a sunny disposition can't be denied, the study notes:

"Neuroticism has been found to be an important risk factor for depression and early mortality. Further, some researchers argue that prolonged negative affect (e.g., depression and anxiety) is linked to disease susceptibility through physiological changes in sympathetic nervous system, hypothalamic-pituitary-adrenal axis, stress hormones, blood pressure, metabolism, and immune function."

The study's findings hew closely to what other researchers have found regarding the link between personality genes and longevity. The George Centenarian Study, the Swedish Centenarian Study and a study done in Japan found that centenarians had a more positive outlook than those in their respective mixed-age population.

The next step for the researchers is a study that will look at people who are the offspring of centenarians and those who aren't "to see the association between longevity phenotype and genotype and personality," Barzilai said. "Then we’ll see if personality is part of living longer. We’ll watch them until they’ll die to see if they’re personality changed or if it was personality that was part of what was important for longevity."

For readers who think they should change their attitudes so they can live longer, Barzilai has this to say: "Yes, everybody [should] become nicer," he laughed. But those are his thoughts "just as a citizen though, not as a responsible scientist."

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