We can do a lot to shorten or lengthen our time on earth, from what we choose to eat, to where we choose to live. But some part of our longevity is hardwired. It’s dictated by our genes.
Scientists have discovered a human “biological clock” based on certain changes to genes, called DNA methylation. These are important for the expression and deactivation of genes, and therefore our development. By studying DNA methylation markers, the researchers found a way to predict lifespan. When people had a biological age greater than their actual age (you could be 50, but have the DNA of a typical 75-year-old), they could see they were more likely to die sooner than a person whose biological and real ages were similar.
Some DNA methylation changes are lifestyle-related, but enough are hereditary for forecasting purposes. “The difference between DNA methylation age and chronological age predicts mortality risk over and above a combination of smoking, education, childhood IQ, social class, APOE genotype, cardiovascular disease, high blood pressure, and diabetes,” says a paper summarizing the work.
The conclusion is based on four separate studies of nearly 5,000 people over a 14-year period. The researchers, who come from several universities in Britain, Australia and the U.S., took blood samples at the beginning of the study then at regular intervals, observing methylation changes. When the biological and chronological ages were five years apart, people had a 21% higher mortality risk, after adjusting for age and gender.
“The same results in four studies indicated a link between the biological clock and deaths from all causes,” says Riccardo Marioni, at the University of Edinburgh, in Scotland. “At present, it is not clear what lifestyle or genetic factors influence a person’s biological age. We have several follow-up projects planned to investigate this in detail.”