In investigating the influence of genetics on longevity, studies over the past two or three decades have found a relatively modest impact of between 15 and 33 percent.
But new research published in the journal Science suggests those estimates were likely skewed by the historical era in which the data was collected and that the impact of genes on longevity could be much higher.
Previous twin and family studies relied heavily on data from people born in the late nineteenth and early twentieth centuries, when deaths from causes unrelated to biological aging — things like infections, accidents, violence, and natural disasters — were 10 times more common than today, says first author of the new study, Ben Shenhar, a doctoral candidate and researcher at the Weizmann Institute of Science in Rehovot, Israel.
Those historical conditions created misleading signals, he says. “You would sometimes see twins where one died at age 30 and the other lived to 95. Today, that would be extremely unusual, but back then it wasn’t.”
To get a more accurate assessment, Shenhar and his colleagues developed a mathematical modeling approach designed to separate deaths caused by external events from deaths driven by biological aging.
When they applied that model, the picture changed substantially. The researchers estimate that inherited genetic factors account for roughly 50 percent to 55 percent of expected lifespan — about double earlier estimates.
“This study convincingly showed that earlier estimates of the genetic contribution to lifespan were too low,” say Charles Brenner, PhD, Alfred E. Mann Family Foundation Chair in the Department of Diabetes and Cancer Metabolism at the Beckman Research Institute of City of Hope in Duarte, California, and wasn’t involved in the research.
The findings also confirmed earlier research on the powerful role that genetics play in dementia: “They found the heritability of deaths from dementia is around 70 percent,” says Dr. Brenner.
On the other hand, up to 45 percent of dementia cases may be preventable through healthy lifestyle choices, including diet and exercise, which just goes to show: Genes do not dictate exactly how long a person will live — but inherited risk may shape the overall range of aging-related lifespan more than scientists once believed.
“Our findings do not suggest that lifestyle is not important for longevity, not at all. Even if 50 percent of lifespan is heritable, that still leaves another 50 percent,” says Shenhar.
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