WASHINGTON (Reuters) – Many factors influence lifespan, including diet, exercise, smoking, alcohol, environment and other variables. It will also prevent you from being run over by a dump truck. But what about your genes? It’s been a controversial question for decades.
A new study points to a larger role for genetics than previous studies had indicated, estimating that genes contribute about 50% to determining human lifespan. This is approximately double what previous studies concluded and reflects the results of lifespan studies in laboratory animals.
“Lifespan is undoubtedly shaped by many factors, including lifestyle, genes and, importantly, randomness. Take, for example, genetically identical organisms raised in similar environments that die at different times,” said Ben Shenhar, a physics doctoral student at the Weizmann Institute of Science in Israel and lead author of the book. the study It was published Thursday in the journal Science.
“In our study, we tried to figure out how much variation between different people can be attributed to genetics. In our study, we tried to split longevity factors into genetics and ‘everything else.’ “Everything else” is about 50% of the pile. ”
The researchers sought to account for confounding factors in previous studies using Swedish and Danish twins, most of which date back to the 19th century. These twin studies did not take into account deaths from violence, accidents, infections, or other factors originating outside the body (called extrinsic deaths), which the authors of the new study said distorts previous research on the genetic component of longevity.
Previous data did not list the cause of death, only the age at death. Therefore, if one twin dies from natural causes at age 90 and the other twin dies at age 30 from an infectious disease such as typhus or cholera rather than from natural causes, data lacking the cause of death may give a misleading impression about the role of genetics in longevity.
A new study employed a mathematical formula to account for extrinsic mortality in twins. Shenhar said that before the era of antibiotics, when the twins in the study were alive, extrinsic mortality was 10 times higher than it is today, but that the main cause was infections that are now easily treated.
The researchers then tested the prediction that external causes of death mask heritability using more recent data from Sweden, which included twins raised together and twins raised separately, that had not been analyzed previously. This analysis actually found that heritability increased as extrinsic mortality decreased.
“Identical twins raised separately share genes but not environment. This helps us distinguish between heredity and environment, nature and nurture,” said Yuri Aron, a systems biologist at the Weizmann Institute and lead author of the study.
Fraternal twins are also valuable in such studies because they share about half of their genetic makeup.
“Previous twin studies have used statistical methods that work well for other traits, such as height, blood pressure, and personality traits, which are not affected by extrinsic mortality,” Aron said.
“However, life expectancy is the only special trait that is strongly affected by extrinsic mortality. In classic twin studies, the cause of death was not recorded, so it was not corrected for,” Aron said.
This conclusion could have implications for aging research.
“Low heritability estimates may have hindered funding and research into the genetics of aging, suggesting that it is primarily random or environmental. Our study validates the search for genetic causes of longevity and shows that the genetic signal, while strong, was previously masked by ‘noise’ in the data,” Shenhar said.
Genes influence lifespan in both directions. On the other hand, there are debilitating genetic defects that can cause disease and shorten lifespans. Meanwhile, genes have been identified that appear to have benefits for longevity.
“Many centenarians reach 100 without any serious medical conditions,” Shenhar said. “It is clear that these people have protective genes that protect them from developing diseases that naturally occur with age. Some of these genes have been identified, but like most complex traits, longevity is likely influenced by hundreds, if not thousands, of genes.”
