Why do some people live very old and others don’t? This question concerns humanity. For a long time, researchers assumed that genes only played a minor role. Lifestyle, environmental conditions or even the social situation are more important, meaning, for example, access to low-pollutant air, clean drinking water and to nature, a healthy diet and enough exercise. But now ask a new study the previous weighting is in question.
The Study
An international research team has reanalyzed data from twin studies in Sweden and the United States. Several thousand pairs of twins born between the late 19th and early 20th centuries were examined. Since identical twins are genetically almost identical, researchers can draw conclusions about the genetic contribution by comparing their lifespans and causes of death.
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Unlike previous work, the researchers in this study not only looked at the actual age of death, but also differentiated between two types of causes of death: intrinsic and extrinsic. External causes of death can affect people of any age – such as a traffic accident or an infectious disease – and have little to do with genetic predisposition. If they are not taken into account, the influence of environmental factors appears greater than it actually is for the biological aging process.
The team therefore used a mathematical model to isolate so-called intrinsic mortality, i.e. mortality that is due to aging and age-related diseases. The result: around 50 to 55 percent of the differences in human lifespan could probably be explained genetically. This is significantly higher than previous estimates, which were 20 to 25 percent.
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What’s the point?
“Within these biological limits, however, there remains a lot of leeway,” says biologist Chiara Herzog from King’s College London, commenting on the new study opposite the Science Media Center. The results therefore do not mean that our age is genetically determined. Calculated heritability is a statistical value for populations, not a prediction for individual people. Little changes in everyday life either. Lifestyle and social factors remain relevant. “The results of this work will definitely not make me to smoke againsays Steve Hoffmann, bioinformatician at the Leibniz Institute for Aging Research in Jena.
These results can still be important for research. They show that previous studies may have underestimated the genetic influence because they did not sufficiently take external causes of death into account. In the long term, this could help to better understand the biological processes of aging.