Living to 100

About one in 10,000 people seems to be a "slow ager" who lives to 100 -- sometimes even in spite of bad health habits, like smoking or exercising little, according to new research. Will you be among them? You won't know if you're among the genetically predisposed for sure, of course, until those 100 birthday candles are lit. But researchers are discovering more and more clues as to who's on his or her way.

Clue #1: How many elderly relatives are on your family tree?

What it may mean: You may have longevity genes.

At least half of all those who reach 100 have a parent, sibling, or grandparent who has also achieved very old age (90-plus), according to the New England Centenarian Study at the Boston University School of Medicine, which studies 100-plussers to unlock secrets of successful aging.

A 2002 study by the center's director, geriatrician Thomas Perls, found that male siblings of centenarians have a 17 times greater chance of reaching their 100th birthday than other men born around the same time; female siblings are 8.5 times more likely to hit 100 than other females also born around the same time.

Other studies have found that exceptional aging is often clustered among multiple first-tier family members, supporting a genetic link. Having siblings, parents, and grandparents who make it to 100 seems to be a much stronger indicator than counting cousins and other more distant relatives.

Clue #2: How fast and how far can you walk?

What it may mean: You're in good condition for the long haul.

Faster walkers live longer. University of Pittsburgh researchers crunched numbers from nine different studies including almost 35,000 subjects ages 65 or older. The result: For each gait speed increase of 0.1 meters per second came a corresponding 12 percent decrease in the risk of death.

The average speed was 3 feet per second (about two miles an hour). Those who walked slower than 2 feet per second (1.36 miles per hour) had an increased risk of dying. Those who walked faster than 3.3 feet per second (2.25 miles per hour) or faster survived longer than would be predicted simply by age or gender.

A 2006 report in the Journal of the American Medical Association found that among adults ages 70 to 79, those who couldn't walk a quarter mile were less likely to be alive six years later. They were also more likely to suffer illness and disability before death. An earlier study of men ages 71 to 93 found that those who could walk two miles a day had half the risk of heart attack of those who could walk only a quarter mile or less.

Clue #3: Do you have a lot of people in your life?

What it may mean: Social engagement is a key lifespan-extender.

Countless studies have found that social isolation is bad for your health, while having friends and social engagement is good. One of the more surprising findings in The Longevity Project (a book about an eight-decade study of 1,500 subjects all born around 1910) is that religious women lived longer -- primarily, as it turned out, because of the social connectedness of their faith-based lifestyle. That is, they worshipped with others, joined committees, and engaged in social outreach, from clothing drives to soup kitchens.

"There was a clear, similar trend among people who had civic engagements, were active in their communities, volunteered, and otherwise stayed connected, whether with families, friends, or coworkers," says Leslie R. Martin, a professor of psychology at La Sierra University in Riverside, California, who's the coauthor of The Longevity Project.