Among people who smoke but never develop lung cancer, researchers found an inherent advantage. The cells that line their lungs appear to be less likely to mutate over time.

The findings suggest that DNA repair genes are more active among some individuals, which can protect against cancers arising, even when cigarettes are regularly smoked.

The study made use of genetic profiles taken from the bronchi of 14 never-smokers and 19 light, moderate, and heavy smokers.

Surface cells collected from the lungs of the participants were sequenced individually to measure mutations in their genomes.

“These lung cells survive for years, even decades, and thus can accumulate mutations with both age and smoking,” explains epidemiologist and pulmonologist Simon Spivack from the Albert Einstein College of Medicine.