NEW DELHI: You might follow the perfect diet, maintain a rigorous exercise routine, and avoid every unhealthy habit, yet your genetic blueprint could still play a decisive role in determining how long you live. A landmark new study has revealed that nearly half of human lifespan is governed by genetics, upending the conventional wisdom that lifestyle and environmental factors are the primary drivers of longevity.
Genetics Accounts for 55% of Lifespan Variation
Published in the prestigious journal Science, this comprehensive research demonstrates that when deaths resulting from accidents, infections, and other external factors are excluded, approximately 55% of human lifespan is heritable. This means that more than half of the observed differences in longevity across populations can be attributed to genetic factors. This proportion is significantly higher than previous estimates, which typically ranged from 10% to 25%. The study was officially released on January 29, marking a pivotal moment in our understanding of ageing.
How the Study Uncovered Genetic Influence
The findings are based on an extensive analysis of over a century of lifespan data, drawing from large Scandinavian twin cohorts in Denmark and Sweden. Researchers meticulously examined identical and non-identical twins who were raised together and apart, as well as siblings of US centenarians. Most participants were born between 1870 and 1935, a period characterized by high mortality rates due to infectious diseases and accidents.
By distinguishing between "extrinsic" deaths—those caused by external events—and deaths linked to biological ageing, the study uncovered that the true impact of genetics on longevity had previously been obscured. Once these external causes were accounted for, the similarities in lifespan between identical twins became markedly stronger. This approach also helps clarify why the genetic influence on lifespan appears more pronounced in contemporary times. As deaths from infections, violence, and accidents have decreased over the decades, the role of genes in determining longevity has become increasingly visible.
Indian Experts Weigh In on Public Health Implications
Indian health experts emphasize that these findings carry significant public health implications. Dr. Anoop Misra, Chairman of Fortis C-DOC, acknowledged that genetics plays a major role in biological ageing but cautioned that Indian conditions might undermine this genetic advantage.
"About half of human lifespan is genetically determined once external causes are excluded, but poor nutrition, air pollution, and the rising prevalence of diabetes and obesity can override genetic advantages and accelerate biological ageing," he stated.
Dr. Ambrish Mithal, Group Chairman of Endocrinology and Diabetes at Max Healthcare, explained that longevity reflects a delicate balance between inheritance and environment. "Genetics provides a broad upper limit for lifespan, while epigenetics and lifestyle determine how close one comes to that limit," he said, noting that environmental factors can activate or deactivate genes without altering the DNA sequence itself.
Genes Set the Ceiling, Environment Determines Reach
Scientists are quick to clarify that these findings do not imply lifespan is fixed at birth. Nearly half of lifespan variation is still influenced by lifestyle choices, access to healthcare, and living conditions. However, the study suggests that genes establish the biological ceiling for longevity, and the environment determines whether individuals can reach that potential.
Researchers believe these insights could reshape ongoing debates about ageing and longevity, while reinforcing the urgency of addressing risks that shorten biological lifespan. This new understanding underscores the importance of integrating genetic insights with public health strategies to promote healthier, longer lives.
