Harriet Bennish, 56, has lived with no such easy assumption. She feels she dodged a bullet early on -- an infected cyst, discovered shortly after her first pregnancy, that required the removal of a kidney. Since that brush with serious illness, the Long Beach singer and actress has made it a point to exercise daily and eat a mostly vegetarian diet in order to stay as healthy as she can.
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FOR THE RECORD:
Aging: An article in the Oct. 15 Health section identified Dr. Moira Fordyce of Stanford University School of Medicine as a gerontologist, someone with a degree in aging studies who does not practice medicine. Fordyce is a geriatrician, a licensed medical doctor specializing in geriatrics. —
But although the specter of genes looms large in the popular imagination, they can be warning posts, not destiny. "The heritability of human life span is actually rather low," says Caleb Finch, professor of gerontology at the University of Southern California.
Even identical twins, once they're in their 70s -- an age that most Americans reach -- are no more likely to die of the same disease than any other two people, he says.
"The genetic influences account for about 30% of aging problems," says Dr. Moira Fordyce, gerontologist at Stanford University School of Medicine. "The other 70% comes from lifestyle."
The contribution of genes does wax and wane. We face specific risks depending on our age. From early to mid-adulthood, those risks are based largely on chance and genetics. For people who make it to late adulthood, the risks come down to the biological aging process, known as senescence, that all humans experience.
But even from one's 30s to one's 60s, when premature death is often linked to genes through a predisposition to cancer or other disease, the land mines of inheritance often can be avoided.
A family history of early heart attack, for example, is a strong motivator to exercise, control weight and take blood pressure and cholesterol-lowering drugs if necessary, all of which can even the playing field.
A family history of cancer is good reason to take every preventive step possible, including routine screenings.
EARLY deaths are always tragic, sometimes with no more comforting explanation than the hand of fate. Infants and children die of birth defects, SIDS, pregnancy complications and rare childhood cancers.
By adolescence, the leading causes of death are violent: accidents, suicide and murder.
Cancer is an especially insidious threat in midlife. In a June 2003, study in the Journal of Gerontology, Finch and colleagues in Paris looked at patterns of mortality in two distinct age groups of French citizens: 30 to 54 and 65 to 89. They found that in the younger group, the proportion of cancer deaths increased markedly in the 30s, 40s and 50s, accounting for 45% of deaths around age 60.
(There were far more total cancer deaths at older ages, but since there were also vastly more deaths in old age, cancer accounted for less than 15% of deaths at ages 85 to 89 and only 5% of deaths among centenarians.)
A similar pattern holds in the United States for cancer and heart disease, according to 2003 data from the government's National Center for Health Statistics. And that is why almost everyone in their 50s and 60s has had the shocking news that a friend or relative their age has died an early death from these causes.
(Again, there were many more total cancer and heart disease deaths among the elderly, but they account for a smaller percentage.)
By the mid-30s, there's a definite fork in the road leading to two fundamentally different paths. Luck is still a player on each path, in the guise of genetic predisposition to disease or lack thereof.