DNA could provide a clue to life expectancy

 Popular culture and media have long toyed with how humans might wrestle with knowing the exact date they were going to die.

The 2011 film Time deals with this idea by focusing on a society in which people wear clocks on their arms that show how much time they have left to live. The British film Knowing also grapples with this dilemma by portraying a world where people know of events that result in mass deaths before they occur.

It turns out that the existence of such a clock may not just reside in the realm of fantasy and science fiction. It exists in the building blocks of every one of us: our DNA.

Scientists from the University of Edinburg

h, Harvard University, the University of California at Los Angeles (UCLA), Boston University and Hopkins, in a collaborative international study published a paper in the journal Genome Biology on the topic of biological clocks.

According to their findings, a biological clock ticks in our very own blood and DNA, predicting when we may die before we are even born.

Scientists can record the “time” of this clock by measuring the amount of DNA methylation present. DNA methylation is the process by which molecules, known as “methyl groups,” are added to DNA.

To study the effects of methylation, scientists retrieved blood samples from 5,000 elderly people over the course of up to 14 years. They gave each person a “biological age” based on the methylation present in blood samples and followed participants for years throughout the study recording when they experienced illness and death.

To measure DNA methylation, the scientists retrieved two sets of epigenetic markers from each person. These markers are inherited traits that have long been associated with increased risk of mortality. The specific markers which the scientists studied are primarily characterized by the addition of a methyl group to a nucleotide. Methylation levels are biologically inherited, but they can also be influenced by lifestyle and environment.

The scientists found that when this “biological age” was higher than the true age of a person, that person was more likely to suffer an earlier death. The relationship was so strong that it was perceptible, even when taking into account factors such as childhood IQ, education, social class, hypertension, heart disease, diabetes and smoking in the patients. All in all, scientists recorded an increased mortality risk of 16 percent in those whose biological clock ages were five years older than their true ages.

The fact that scientists have discovered a new factor for premature mortality with an even higher correlation than smoking, diabetes and disease undoubtedly has great implications for genomic biology. Such a predictor would be valuable information to healthcare policy.

The discovery of this epigenetic marker could also fund more research into that specific portion of genetic code. Further studies into DNA methylation could eventually discover how to turn “off” the genes which predict preterm mortality.

The first step to stalling aging is discovering the clock. Now scientists are that much closer to finding out how to turn it back.