SAN FRANCISCO (KRON) – A new study published by the American Heart Association finds that more than 7,000 genes can be altered from smoking cigarettes.

Researchers looked at blood samples taken from 16,000 people in past studies.

People who quit smoking had their genes repaired within five years after they stopped, according to the study.

Some people’s genetics stayed the same even 30 years after they quit smoking.

“Although this emphasizes the long-term residual effects of smoking, the good news is the sooner you can stop smoking, the better off you are,” said the author of the study, Dr. Stephanie London.

London works for the U.S. National Institute of Environmental Health Sciences, who conducted the study.