New research has pinpointed a specific genetic variation that may cause smokers to stick with the habit longer than smokers who don’t have the variant. The research, published in the Journal of the National Cancer Institute, also indicated that smokers with the genetic variant are more likely to be diagnosed with lung cancer at an earlier age.

Researchers at Washington University School of Medicine in St. Louis analyzed 24 studies involving more than 29,000 smokers of European ancestry. They concluded that smokers with a particular variation in the nicotine receptor gene, CHRNA5, were more likely to continue smoking for an average of four years after those without the variant kicked the habit. The smokers with the genetic variant were also more likely to receive a lung cancer diagnosis four years earlier than those without the variation. Smokers with the gene variant were also found to inhale more deeply when smoking.

“People with the risk variant average a four-year delay in the age at which they quit smoking,” study author Dr. Li-Siun Chen said in a news release. “Instead of quitting at age 52, which was the average age when study participants with a normal gene stopped smoking, people with the genetic variant quit at age 56.”

Chen said the findings have important clinical implications, as those found to have the genetic variant could undergo screening for lung cancer at a younger age. Chen also noted in previous studies that smokers with the variant responded to medications meant to help them quit smoking.

“The same people with this high-risk gene are more likely to respond to smoking-cessation medications, such as nicotine-replacement patches, lozenges or gum,” Chen said in the release. “Although it’s clear the gene increases the chances a person will develop lung cancer at a younger age, it also is clear that the risk can be reversed without treatment.”

According to the American Cancer Society, lung cancer accounts for 27 percent of all cancer deaths in the U.S. each year. It is the second most common cancer in both men and women excluding skin cancer.