Twin Studies Reveal Genetic Influence on Lifespan Half Point/iStockphoto/Getty Images
In developed and stable nations, individuals’ lifespans are likely influenced not only by environmental factors and lifestyle choices but also by the genetic variations inherited from their parents. This conclusion arises from a recent analysis of data from a Danish-Swedish twin study.
For those residing in such countries, it’s not surprising to learn that genetics may account for half of the variation in lifespan, while environmental factors comprise the other half. However, earlier twin studies conducted decades ago suggested that genes explained only about 25% of the variation in human lifespans.
“The proportion shifts slightly, with genetics playing a more significant role while the environmental impact reduces a bit,” stated Joris Dieren from Leiden University Medical Center, Netherlands. “Nonetheless, environmental factors still constitute a crucial element, accounting for at least 50%.”
Heritability measures the extent to which variations in a specific trait arise from genetic influences as opposed to environmental factors. The research team emphasizes that the heritability of any trait isn’t a constant value applicable universally; rather, it pertains to specific populations in distinct environments.
Height in wheat serves as a classic illustration. If seeds are planted in a flat, consistent field, nearly all height variations will be a result of genetics. Conversely, in a more diverse terrain, most height variation will stem from factors like soil, light, and water conditions. The heritability of height varies significantly in these two contexts.
To estimate human trait heritability, geneticists often compare twins raised in the same environment to those raised apart. In this study, Dieren and his colleagues primarily referenced twins born in Sweden or Denmark between 1870 and 1935.
Excluding accidental deaths and infections, the heritability of longevity spiked to approximately 50%, compared to age-related diseases like heart conditions.
This aligns more with our existing knowledge about aging in animals, as Dieren noted. “I believe the figure is more realistically closer to 50% than 25%.”
“This paper evaluates the heritability of maximum lifespan under optimal conditions, assuming only age-related processes are at play. This is a much narrower focus than overall lifespan,” emphasized Peter Ellis from the University of Kent, UK. It’s unsurprising that this more specific question has a higher heritability rate, he pointed out.
Joao Pedro de Magalhães, a professor at the University of Birmingham, UK, concurs: “The findings are entirely expected.”
This research indicates the potential presence of multiple genetic mutations influencing variations in human lifespans, with the identification of such mutations possibly aiding in the development of longevity-enhancing drugs. Yet, few have been discovered to date.
“The mystery remains as to why so few genes related to human longevity have been identified,” stated de Magalhães.
A significant challenge exists due to the nature of studies like the UK Biobank; many participants are still alive, resulting in insufficient numbers for reliable statistical analysis. Dieren also believes this complexity lies within the genetic factors themselves.
For instance, Ellis pointed out that there could be trade-offs, where a genetic variant that reduces autoimmune disease risk might also impair infection-fighting abilities. This suggests that the researchers’ assumption linking infection-related deaths to lifespan may not be entirely accurate.
De Magalhães added that the role of genetics appears significantly different when contrasting species rather than individual differences within a single species. “Even with the mouse genome, you wouldn’t expect a lifespan beyond three or four years,” he noted. “In stark contrast, the bowhead whale genome can result in lifespans exceeding two centuries.”
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Source: www.newscientist.com
