Smoking cessation is a protective factor for lung cancer onset and mortality: a population-based prospective cohort study

Background Smoking is a pivotal modifiable risk factor for lung cancer (LC). Previous studies have indicated that a smoking cessation program might be incorporated into the LC screening program. However, the effects of smoking cessation and its duration with the age at onset (AAO) of LC, all-cause mortality, and LC-specific mortality remain unclear. We aimed to comprehensively investigate the association of smoking cessation-related behaviors on the AAO of LC, LC-specific and all-cause mortality. Methods A total of 2671 smokers with LC as the primary site from the UK Biobank were included in this study, with a 7:3 ratio assigned randomly to a discovery set (n = 1872) and a validation set (n = 799). Generalized linear regression models were used for AAO of LC outcomes and Cox models for mortality outcomes. Results Participants over 60 years old could still benefit from smoking cessation to prolong AAOs (beta = 1.613 for men, P = 0.003; beta = 1.533 for women, P = 0.018). A cessation duration of > 15 years was associated with a later AAO in men (P < 0.001). Moreover, smoking cessation before 60 years old, especially among those under 40 years, was significantly associated with a lower risk of all-cause mortality (men: hazard ratio (HR): 0.65 [95% confidence interval 0.51-0.83]; women: 0.62 [0.47-0.83]) and LC-specific mortality (men: 0.67 [0.51-0.87]; women: 0.68 [0.50-0.92]). Compared with continuous smokers, former smokers who quit smoking for more than 15 years had a lower risk of all-cause mortality (men: 0.70 [0.59-0.84]; women: 0.68 [0.56-0.84]) and LC-specific mortality (men: 0.71 [0.59-0.87]; women: 0.69 [0.56-0.86]). Conclusions Smoking cessation after 60 years old may still be helpful for a later AAO of LC. Former smokers who quit smoking for more than 15 years have a reduced risk of developing LC and mortality.