Living to very old age may be "in the genes" as the saying goes, and a recent study published in the journal Aging suggests that certain personality traits make up a major part of the mix of longevity genes.

Researchers found that having a positive attitude and a sense of humor could play a role in living a longer, healthier life. They developed a questionnaire designed to identify certain genetically-based personality traits and used it to assess 243 Ashkenazi Jewish adults between 95 and 107 years of age. The investigators chose this population because their genetic similarity would make it easier to account for genetic differences in personality.

"The results indicated they had two things -- a positive attitude for life, meaning they are optimistic, easygoing, extraverted, laughed more and expressed emotions rather than bottling them up," said Dr. Nil Barzilai, a study co-author and director of the Albert Einstein College of Medicine's Institute for Aging Research.

The study participants also were less neurotic and more conscientious than a representative sample of other Americans.

Based on census data, centenarians make up about .2 percent of the U.S. population, but the number has been rapidly increasing, the authors wrote.

Previous research has suggested that the oldest adults may be genetically predisposed to living longer and healthier both physiologically and psychologically and that personality can affect a person's physical health.

"There's an interaction between personality and physiology," said Dr. Gary Small, director of the UCLA Center on Aging. Small was not involved in Barzilai's study, but has done research in this area. "It makes sense that being more positive causes less stress and seems to get people on the right track to live better."

The genes, it turns out, play a less important role in determining longevity.

"Several studies have found that genetics accounts for only about one-third of how long and well we live," said Small, who is also co-author of "The Alzheimer's Prevention Program."

Barzilai added that it's still not known precisely how personality influences longevity.

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Positive Attitude Linked to Long Life