A genetic variant appears to influence the length of telomeres which are caps on chromosomes. These telomere caps shorten with age and the shortening is linked to aging.

Scientists announced today (7 Feb) they have identified for the first time definitive variants associated with biological ageing in humans. The team analyzed more than 500,000 genetic variations across the entire human genome to identify the variants which are located near a gene called TERC.

It is important to note that telomere shortening might offer a life extending benefit: shorter telomeres might stop at least some cancer cells from dividing too many times. The genetic variant that shortens telomeres therefore might have been selected for in some humans.

Shorter telomeres are linked to some diseases of old age.

"What we studied are structures called telomeres which are parts of one's chromosomes. Individuals are born with telomeres of certain length and in many cells telomeres shorten as the cells divide and age. Telomere length is therefore considered a marker of biological ageing.

"In this study what we found was that those individuals carrying a particular genetic variant had shorter telomeres i.e. looked biologically older. Given the association of shorter telomeres with age-associated diseases, the finding raises the question whether individuals carrying the variant are at greater risk of developing such diseases"

Possibly the genetic variant causes telomeres to shorten more rapidly.

Professor Tim Spector from King's College London and director of the TwinsUK study, who co-led this project, added:

"The variants identified lies near a gene called TERC which is already known to play an important role in maintaining telomere length. What our study suggests is that some people are genetically programmed to age at a faster rate. The effect was quite considerable in those with the variant, equivalent to between 3-4 years of 'biological aging" as measured by telomere length loss. Alternatively genetically susceptible people may age even faster when exposed to proven 'bad' environments for telomeres like smoking, obesity or lack of exercise – and end up several years biologically older or succumbing to more age-related diseases. "

A great way to cure cancer that has minimal side effects would open the door for a variety of rejuvenation therapies. Treatments to lengthen telomeres would carry less risk if cancer was easily curable.

Stem cell therapies hold out the hope of working around the telomere shortening problem. Old cells can accumulate dangerous genetic mutations that can lead to cancer. But in the future stem cell lines will be selected to have few harmful mutations and then stem cells with long telomeres can be inserted into the body with the ability to grow and do repairs that cells with short telomeres are unable to do.