Friday, September 01, 2006

Luck of the draw -- life expectancy not as genetically determined as previously thought

People tend to assume their life spans will be roughly the same as those of their parents or other close relatives, but writing in the New York Times, science writer Gina Kolata reports that the latest research suggests this is a myth. Life expectancy is only weakly detemined by one's genes.
Life spans, says James W. Vaupel, who directs the Laboratory of Survival and Longevity at the Max Planck Institute for Demographic Research in Rostock, Germany, are nothing like a trait like height, which is strongly inherited.

“How tall your parents are compared to the average height explains 80 to 90 percent of how tall you are compared to the average person,” Dr. Vaupel said. But “only 3 percent of how long you live compared to the average person can be explained by how long your parents lived.”

“You really learn very little about your own life span from your parents’ life spans,” Dr. Vaupel said. “That’s what the evidence shows. Even twins, identical twins, die at different times.” On average, he said, more than 10 years apart.

The likely reason is that life span is determined by such a complex mix of events that there is no accurate predicting for individuals. The factors include genetic predispositions, disease, nutrition, a woman’s health during pregnancy, subtle injuries and accidents and simply chance events, like a randomly occurring mutation in a gene of a cell that ultimately leads to cancer.
Just how great the influence of those random events can be is illustrated by several examples in the article of people who greatly outlived siblings, parents or other relatives. Some people are just lucky.

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