Smoking Cessation and Lung Cancer Mortality in a Cohort of Middle-aged Canadian Women

Purpose To determine the impact of smoking cessation on lung cancer mortality among women. Methods Survival analysis is used to assess the effect of smoking cessation on lung cancer death in the dietary cohort of 49,165 women aged 40 to 59 years enrolled in the Canadian National Breast Screening Study. Results During an average of 10.3 years of follow-up, 106 women died of lung cancer. The risk of lung cancer mortality among women who quit before age 50 (HR = 0.26; 95% CI, 0.13–0.55 among women who quit at ages 40–49) or quit in the previous 10 years (HR = 0.39; 95% CI, 0.22–0.69) is substantially lower than the risk among current smokers. Women who quit after age 40 or have quit for less than 20 years are at substantially higher risk of lung cancer mortality compared with never smokers. Both duration of smoking cessation and age at quitting have independent effects on lung cancer mortality, after controlling for number of cigarettes smoked per day and number of years smoked, as well as other potential confounding variables. Conclusion These findings suggest that programs and policies to promote early cessation of smoking and prevention of relapse should be a public health priority.