London, Sep 23 (IANS): Dysregulation of the DNA -- an important cause of ageing -- does not take place in some people, while in some individuals, the DNA appears to be youthful despite their advanced years.

This dysregulation of the DNA can act as a precursor to various diseases, including cancer, and on the other hand, youthful DNA may prevent the disease, the researchers have found.

The DNA of young people is regulated to express the right genes at the right time. With the passing of years, the regulation of the DNA gradually gets disrupted, which is an important cause of ageing, the study said.

"The study suggests that the dysregulation of the DNA is a fundamental process that could push the risk of different diseases in the wrong direction," said Bas Heijmans, an epigeneticist at the Leiden University Medical Center in the Netherlands.

Further, in cancer cells changes in the regulation of the DNA at the same sites was found as if the differences occurring with ageing were a precursor of the disease, the study said.

"We therefore want to study whether a dysregulated DNA increases the risk of different forms of cancer and, conversely, a 'youthful' DNA is protective," added Roderick Slieker from Leiden University Medical Center.

For the study, the researchers charted the regulation of the DNA of over 3,000 people by measuring the level of methylation -- a process by which cells control gene activity -- at close to half a million sites across the human DNA.

Not everyone in the study showed equal evidence of an age-related dysregulation of the DNA. They were looking for sites where the difference in regulation increased between people as life progressed.

Some elderly people had DNA that was regulated as if they were still 25 years old. In these individuals, genes characteristic of the ageing process were much less active, the researchers said.

"We believe we may have caught the ageing process in the act. The dysregulation of the DNA that we discovered went hand in hand with higher activity in genes that continuously try to repair damage to cells. This process is not fully effective and in the long run leads to ageing," Heijmans explained, in the research published in the journal Genome Biology.