Scientists have discovered genetic variants that are associated with biological aging, a finding that could explain why some people seem to age faster than others.

The researchers, who report their findings Feb. 7 in the journal Nature Genetics, analyzed more than 500,000 genetic variations in search of those linked to aging.

According to study co-leader Dr. Nilesh Samani, a professor of cardiology at the University of Leicester, there are two forms of aging: chronological (based on how old something is in the traditional sense) and biological (in which cells of some people are older or younger than their chronological age).

"There is accumulating evidence that the risk of age-associated diseases, including heart disease and some types of cancers, are more closely related to biological rather than chronological age," Samani said in a news release from the University of Leicester and King's College London.

Study co-leader Dr. Tim Spector, of King's College London, said in the release that "what our study suggests is that some people are genetically programmed to age at a faster rate."

Due to their genes, he said, some people may age even faster when exposed to things "like smoking, obesity or lack of exercise, and end up several years biologically older or succumbing to more age-related diseases."