Genetics Plays a Bigger Role in Lifespan Than Previously Thought
A recent study suggests that genetics may determine about 50% of a person’s lifespan, which is more than double what earlier research had indicated regarding the heritability of longevity.
This new research, published in the journal Science, utilized a sophisticated mathematical model to arrive at this figure. By focusing on external causes of death—like accidents and infections—the research team was able to refine their estimates by removing these environmental impacts.
Traditionally, scientists have used twin studies to assess the heritability of various human traits. Twin studies compare individuals who share nearly all their DNA to those sharing about half. Identical twins, or “monozygotic” twins, share nearly 100% of their genes, while fraternal twins, or “dizygotic” twins, share around 50%.
The researchers examined how lifespan correlated with genetics in various twin sets, looking for patterns that could indicate genetic influence. According to co-author Joris Deelen, a geneticist at Leiden University in the Netherlands, a strong genetic determination would show a higher correlation for identical twins compared to fraternal twins.
Previous estimates of the heritability of lifespan ranged between 6% and 25%, suggesting that genetics had a limited role in longevity. These figures were significantly lower than those for other complex traits, like psychiatric disorders, where heritability is around 50%.
Observations of families with notably long lifespans and the genetic risks tied to age-related diseases hinted to Deelen and his team that genetics likely played a larger role in longevity than had been assumed.
A Different Perspective on Lifespan
One challenge in this research was to distinguish genetic drivers of death—like age-related diseases—from external factors such as injuries and infections. Although Deelen acknowledged that the line between genetic and external factors can be blurry, they concentrated on commonly treatable diseases like scarlet fever.
“In the past, we always looked at all-cause mortality, but that often overlooked the actual causes of death,” remarked Luke Pilling, a geneticist at the University of Exeter, who was not part of the study.
Deelen’s team, which included geneticists, doctors, and statisticians, created a model that accounted for these external contributors, even in cases where the causes of death were unknown. They analyzed data from twin cohorts in Sweden, Denmark, and the U.S., which included individuals born between 1870 and 1935, and found that heritability estimates consistently hovered around 50%.
Interestingly, the study also looked at Swedish twins born in different decades. This allowed for an analysis of how extrinsic mortality rates changed over time; for example, twins born in 1900 faced very different health risks compared to those born in the 1930s.
Past assessments of lifespan heritability likely indicated an increase over those decades, as genetic factors began to play a more prominent role. The new model, however, offers consistent estimates regardless of external factors.
Of course, no model is without its limitations. “Ideally, we would have a cohort where we can directly identify causes of death as intrinsic or extrinsic,” Deelen said, noting the lack of such data available at the moment.
The model has so far primarily been tested on individuals of Northern European descent, which raises questions about its applicability in other parts of the world.
Modern recordkeeping might shed light on these issues in the future. But what does this research mean for healthcare? Understanding the genetic elements that contribute to longevity could reshape geriatric medicine, especially as aging populations become increasingly common.
“If we can grasp the biological mechanisms behind longer, healthier lives, we might devise strategies to encourage those pathways,” Pilling stated. “This finding will definitely influence my research.”
Importantly, though, the 50% heritability estimate doesn’t doom anyone to a short life or guarantee a long one. Deelen emphasized that while genetics play a role in determining lifespan, environmental factors and lifestyle choices are still crucial.
“This suggests there’s a genetic tendency towards longevity, but what you choose to do and where you live matters just as much,” he clarified. “Optimizing your lifestyle remains essential.”
