How can some of the world's oldest people also lead unhealthy lives?

Hard-living Centenarians Defy Science

Jeanne Calment at age 120.
Jeanne Calment at age 120.
AP Photo/Launette

­There have been cases in which the world's oldest people -- and we're talking way over 100 years old -- have also lived thoroughly unhealt­hy lives. Centenarians (people who are 100 years of age or older) like Madame Jeanne Calment, who smoked until she was 100 and died in 1997 at age 122, aren't supposed to live as long and certainly not in good health, as Calment did. They're supposed to live like fitness guru Jack LaLanne, who himself is holding steady at age 94, and is healthy enough to play Hercules in the 2006 TV movie "The Year Without a Santa Claus" at age 92.

LaLanne's longevity is self-explanatory; he drinks fresh juice each day and worships at the temple of fitness. But a 100-year-old who smokes and is still alive -- healthy and happy, even -- defies science. Why aren't people like Calment riddled with cancer or felled by heart disease? Why aren't they hooked up to all manner of life-support devices and kept alive by the sheer will of their physicians?

Those questions led some scientists to investigate these inexplicably long lives. The race toward discovering the key to this type of longevity still continues. However, scientists have figured out that somewhere within our genetic makeup, some of us appear to have a mutation -- a leg up, really -- that staves off cellular death. It's also possible that if researchers can identify the gene or genes responsible for long life, the rest of us can benefit through gene therapy.

Enough with the questions; let's get to some science, shall we?