We Were Wrong About How Much Your Genes Shape Your Lifespan - ScienceAlert

Putting aside the risk of an early grave by accident or injury, your genes may have a much greater impact on your lifespan than previously thought, according to an unparalleled study of twin data. The recent analysis, led by researchers from the Weizmann Institute of Science in Israel, suggests that around 55 percent of the variation in human lifespans is influenced by genes. That's much higher than previous estimates of around 20-25 percent, with measures falling as low as just 6 percent in some studies. The findings have implications for our understanding of genetic aging and the search for genes specifically associated with longevity, according to the researchers. "For many years, human lifespan was thought to be shaped almost entirely by non-genetic factors, which led to considerable skepticism about the role of genetics in aging and about the feasibility of identifying genetic determinants of longevity," says molecular biologist Ben Shenhar, from the Weizmann Institute of Science. All the myriad ways in which human life can come to an end can be put into two categories: intrinsic and extrinsic. Intrinsic deaths are driven by internal factors like aging and genetics, while extrinsic deaths cover accidents, infections, and other outside causes. In much of the historical data used in earlier studies, causes of death weren't captured in sufficient detail, making it hard to distinguish the different factors. Here, the team analyzed data on thousands of twins, including data on siblings raised apart, which had not been considered in lifespan heritability studies before. Twin data is crucial for genetic studies, separating the effects of genes on an individual from everything that comes after birth such as lifestyle choices, diet, and education. Extrinsic causes of death were sifted out using mathematical models of mortality that suggest deaths are more likely to be intrinsic the older we get. Not only did the results closely match real-world data, but the new estimate of 55 percent is also closer to existing estimates on genes accounting for variations in other aspects of our physiology, such as height. "Such high heritability is similar to that of most other complex human traits and to life-span heritability in other species," write the researchers in their published paper. While the new research doesn't necessarily counter earlier studies, it does suggest that the data we've used previously haven't told the full story when it comes to the balance of life and death. Related: Something About Brazil's Oldest People May Reveal Missing Clues on Longevity The researchers are now seeking to test their conclusions against modern datasets that do a better job of separating different causes of death. Learning that genetics has such significance in determining lifespan raises questions on which genes have the most effect and how they work – two possible areas for future research. "If heritability is high, as we have shown, this creates an incentive to search for gene variants that extend lifespan, in order to understand the biology of aging and, potentially, to address it therapeutically," says Shenhar. The research has been published in Science.