Scientists think they may have unlocked a key secret to long life – quite simply, genetics, according to The Guardian.
Writing in the journal Science, the researchers described how previous studies that had attempted to unpick the genetic component of human lifespan had not taken into account that some lives were cut short by accidents, murders, infectious diseases or other factors arising outside the body. Such “extrinsic mortality” increases with age, as people often become more frail.
Prof Uri Alon and colleagues at the Weizmann Institute of Science in Israel say the true genetic contribution to the variation in human lifespan has been masked.
The team looked at “heritability,” the proportion of change in a characteristic such as height, body weight or lifespan within a population that can be attributed to genetics rather than environmental factors. Previous studies for human lifespan have thrown up a wide range of values – with heritability ranging from 6% of the variation to 33%.
But Alon, who co-authored the research, and his colleagues said such figures were underestimates. “I hope this will inspire researchers to make a deep search for the genes that impact lifespan,” The Guardian quoted Alon as saying. “These genes will tell us the mechanisms that govern our internal clocks.
“These can one day be turned into therapy to slow down the rate of ageing and in that way slow down all age-related disease at once.”
The team created a mathematical model that takes into account extrinsic mortality and the impact of biological ageing, and calibrated it using correlations of lifespan from historical datasets of thousands of pairs of twins in Denmark and Sweden.
They removed the impact of extrinsic mortality to reveal the signal from biological ageing, which is caused by genetics. The results suggest about 50% of the variation in human lifespan is due to genetics – a figure the researchers said was on a par with that seen in wild mice in the laboratory.
The other 50% of variation in human lifespan, they said, was probably explained by factors such as random biological effects and environmental influences.
