The keys to living long and well

In the Harvard study, 2,357 men from the Physicians' Health Study with an average age of 72 were followed for 25 years, during which they regularly answered questionnaires on their health and habits. Among the group, 970 men lived to at least 90.

A man who didn't smoke, didn't have diabetes, wasn't overweight, had normal blood pressure, and exercised two to four times a week had a 54 percent probability of living until 90. Each healthy behavior crossed off the list sent the probability down. Men who were sedentary, had high blood pressure, were overweight, and smoked had only a 4 percent chance of living until 90.

"It's not surprising that these (factors) might be associated with lifespan and health, but it's reassuring that these same factors continue to make a difference in older years," lead author Dr. Laurel B. Yates, also of Brigham and Women's Hospital, said in an interview, noting that exercise's effects shade into other factors. "It's kind of a threesome: get more years, better years, and better function."

In the centenarian study, Dr. Dellara F. Terry's team of researchers began with a hypothesis that surviving until 100 meant delaying or never getting such illnesses of aging as chronic obstructive pulmonary disease, cardiovascular disease, diabetes, osteoporosis, or Parkinson's disease. But when they looked at a study of 739 people who had lived to age 97 or older, they found that almost one-third of the survivors had developed these illnesses by age 85 -- but were not disabled by them. They also report that men had better mental and physical function than the female centenarians, which they say is consistent with other studies.

"One explanation for this may be that men must be in excellent health and/or functionally independent to achieve such extreme old age," the authors write. "Women on the other hand may be better physically and socially adept at living with chronic and often disabling health conditions."