A new study has revealed that smoking affects one's DNA permanently, negating the earlier theory that the effects of the habit fade away after five years of quitting. The study has been published in the journal Circulation: Cardiovascular Genetics earlier this week.

Researchers in the study examined 16,000 people and found that the methylation process, which changes the DNA, and can either inactivate a gene or alters the way it functions, reported NBC. This, in turn, can lead to heart disease and cancer. Roby Joehanes of Hebrew SeniorLife and Harvard Medical School said while most genes return to their original state after five years of quitting, changes in 19 genes among smokers are almost irreversible and can last 30 years.

Joehanes added that most of the 7,000 genes affected by smoking are linked to heart diseases and cancer. "Our study has found compelling evidence that smoking has a long-lasting impact on our molecular machinery, an impact that can last more than 30 years," he said.