People who live to a ripe old age may not eat better, exercise more or smoke less than others, a new U.S. study suggests.

For the study, investigators interviewed 477 people who were living independently and were 95 and older who were participating in a longevity research project that is trying to understand why centenarians live as long as they do.

Overall, those with exceptional longevity did not have healthier habits than the comparison group. (Rick Roach/The Reporter/Associated Press)

The elderly participants were asked about their lifestyles at age 70, which was considered to reflect the lifestyle they'd followed for most of their adult lives, such as whether they drank alcohol, smoked tobacco, exercised and what they ate.

To compare these long-lived folks to the general population, the researchers used data from 3,164 people who had been born around the same time as the centenarians and were examined between 1971 and 1975 as part of a national survey.

Overall, those with exceptional longevity did not have healthier habits than the comparison group in terms of body mass index, smoking, physical activity or diet, the researchers reported in Wednesday's online issue of the Journal of the American Geriatrics Society.

In some ways, the old-timers showed less healthy behaviour than the others. About 43 per cent of the men who lived to be at least 100 exercised regularly, compared with 57 per cent in the control group.

"Although this study demonstrates that centenarians can be obese, smoke and avoid exercise, those lifestyle habits are not good choices for most of us who do not have a family history of longevity," said study author Dr. Nir Barzilai, a professor of medicine and of genetics at Albert Einstein College of Medicine in Bronx, N.Y.

"We should watch our weight, avoid smoking and be sure to exercise, since these activities have been shown to have great health benefits for the general population, including a longer lifespan," he added in a release.

About three-quarters of those in the long-lived group were women.

The centenarian participants were also Ashkenazi Jews. The researchers said Ashkenazi Jews are more genetically uniform than other populations, which makes it easier to spot gene differences that are present.

When the researchers asked participants why they believed they had lived so long, one-third reported a history of family longevity, while 20 per cent believed that physical activity also played a role.

Other factors given included:

• Positive attitude (19 per cent).
• Busy or active life (12 per cent).
• Less smoking and drinking (15 per cent).
• Good luck (eight per cent).
• Religion or spirituality (six per cent).

The research was supported by grants from the U.S. National Institute on Aging.