• Department of Oncology, University of Alberta, Cross Cancer Institute, Edmonton, Alberta, Canada; Clinical Oncology Department, Faculty of Medicine, Ain Shams University, Cairo, Egypt. Electronic address: omar.abdelsalam@ahs.ca.

PURPOSE: To assess the impact of secondhand smoking on the incidence and mortality of lung cancer among never smokers enrolled onto the Prostate, Lung, Colorectal, and Ovary (PLCO) study.

PATIENTS AND METHODS: Deidentified data sets from the PLCO study were accessed and never smokers who completed the supplementary questionnaire's questions related to history of exposure to secondhand smoking were included in the current study. Multivariate Cox regression analysis was conducted to evaluate the impact of adulthood and childhood secondhand smoking on lung cancer incidence and mortality.

RESULTS: A total of 49,569 participants were included in the current analysis. Using multivariate Cox regression analysis, participants with secondhand smoking most of their work time had a higher risk of lung cancer diagnosis (hazard ratio, 2.038; 95% confidence interval, 1.313-3.164; P = .002). Likewise, participants with secondhand smoking most of their adult living time had a higher risk of lung cancer diagnosis (hazard ratio, 1.809; 95% confidence interval, 1.161-2.819; P = .009). Moreover, participants with secondhand smoking most of the adult time had a higher risk of death from lung cancer (hazard ratio, 1.925; 95% confidence interval, 1.035-3.575; P = .038). Participants with secondhand smoking most of the adult time were also more likely to have had hypertension (P < .001), diabetes mellitus (P < .001), heart attack (P < .001), stroke (P = .028), chronic bronchitis (P < .001), and emphysema (P < .001).

CONCLUSION: Never smokers with a history of adult secondhand smoking had a higher probability of a subsequent diagnosis of lung cancer. Likewise, never smokers with a history of adult secondhand smoking were more likely to die from lung cancer.