Secret of youth may be in your genes

Our DNA may hold the answer to how quickly we age, a new study suggests. File photo / Glenn Jeffrey

A genetic test for how quickly a person will age over the course of a lifetime may soon be possible, following a study that has for the first time identified DNA variations in the population that can be linked with biological ageing.

Scientists found that people who inherit two copies of a particular DNA variant - about 7 per cent of the population - show the biological signs of being about eight years "older" than people of the same age who carry neither genetic variant.

The findings are important because they could lead to more sophisticated ways of determining the likely chances of a young person ageing significantly more quickly than the average, and therefore being more prone to age-related illnesses such as coronary heart disease and senile dementia.

The study supports the idea that ageing is based not just on straight- forward chronology and environmental factors (such as smoking or heavy drinking) but on biology as well - some people are born with a genetic pre-disposition to age more quickly.

It could explain why some people look older for their years than their contemporaries of the same age, even though they may not engage in activities that are known to accelerate the ageing process, such as smoking and supporting Millwall.

Individuals who have inherited just one copy of the genetic variation - about a third of the population - are on average about four years "older" than their contemporaries, as revealed by analysing the individual's chromosomes for a recognised sign of biological ageing.

"The motivation behind this study was the evidence from coronary research showing that some people who are in their 80s have completely normal arteries but others in their 40s, with no obvious risk factors, have diseased arteries. The difference seems to be biological," said Nilesh Samani, professor of cardiology at Leicester University.

"There is accumulating evidence that the risk of age-associated diseases, including heart disease and some types of cancers, is more closely related to biological rather than chronological age," Professor Samani said.

The researchers focused on the structure at the tips of chromosomes, called a telomere, which gets progressively shorter as someone grows older.

The telomere plays a critical role in cell division and ageing and has been likened to the plastic caps at the end of shoelaces which keep them from fraying.

Nearly 3000 people of varying ages took part in the study. Their telomeres were measured from blood samples and their entire genomes were analysed for DNA variations that could be linked with shorter-than-average telomeres.

"Individuals are born with telomeres of certain length, and in many cells telomeres shorten as the cells divide and age," Professor Samani said.

"We found that those individuals carrying a particular genetic variant had shorter telomeres, that is [they] looked biologically older."

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