Unlocking the Mystery of Long Life: The Role of Genetics
The quest for longevity has captivated scientists and individuals alike, with many attributing it to a variety of factors, from a nightly drink of whiskey to a life free of trouble. Now, a groundbreaking study published in the journal Science suggests that the secret to a long life might be more straightforward: genetics.
Prof. Uri Alon and his team at the Weizmann Institute of Science in Israel have made a remarkable discovery. They argue that previous studies, which aimed to unravel the genetic component of human lifespan, overlooked a critical aspect: the impact of external factors on mortality. These "extrinsic mortality" factors, such as accidents, murders, and infectious diseases, can significantly affect lifespan, especially as individuals age and become more vulnerable.
The team's research reveals that the true genetic contribution to human lifespan has been obscured by these external influences. By developing a sophisticated mathematical model, they accounted for extrinsic mortality and biological aging, and then calibrated it using extensive data from historical twin studies in Denmark and Sweden.
Their findings indicate that approximately 50% of the variation in human lifespan can be attributed to genetics, a figure comparable to that observed in laboratory-studied wild mice. The remaining 50% is likely influenced by random biological factors and environmental conditions, including lifestyle choices, diet, exercise, social interactions, and environmental conditions.
Ben Shenhar, a co-author of the study, emphasizes the importance of these external factors, stating, "That’s where we would expect to find all the usual suspects – lifestyle, diet, exercise, social relations, environment, and more." As we age, these external influences are expected to become even more significant.
The study's results were further validated using data from a US study of siblings of centenarians, consistently showing a heritability of lifespan around 50%. Additionally, when the team analyzed another Swedish dataset, they observed that as extrinsic mortality decreased over the 20th century due to public health improvements, the estimated genetic contribution to lifespan increased, reinforcing the idea that extrinsic mortality plays a crucial role in heritability.
Shenhar also highlights the day-to-day relevance of genetics in longevity. He notes that around 20% of centenarians reach their age without any serious debilitating illnesses, suggesting that their genes may have a protective effect. The team's ongoing efforts to identify these protective genes are promising, although many remain undiscovered.
While the study doesn't consider the immune system's genetic influence, Prof. Richard Faragher of the University of Brighton points out that the research aligns with the heritability of lifespan in other species. This similarity is significant because it suggests that interventions effective in mice may also benefit humans, providing a solid foundation for future research and potential therapies to combat aging and age-related diseases.
