Background and aim: Active smoking is well known to be a risk factor for colorectal neoplasia (CRN). However, it remains unclear whether passive smoking is also related to the risk of CRN. This study investigated the effect of passive smoking on the risk of CRN in never, former, and current smokers.
Methods: A cross-sectional study was performed on asymptomatic examinees who underwent colonoscopy as part of a health check-up.
Results: Of 136 707 participants, 33 052 (24.2%) were never passive smokers, and 103 655 (75.8%) were ever passive smokers. The mean age of the study population was 41.0 years. The proportion of never, former, and current smokers was 56.9%, 21.4%, and 24.8%, respectively, and the proportion of overall CRN and advanced CRN (ACRN) was 15.4% and 1.7%, respectively. Ever passive smoke exposure was associated with an increased risk of overall CRN in never smokers (adjusted odds ratio [AOR] 1.08; 95% confidence interval [CI] 1.02-1.13) and former smokers (AOR 1.08; 95% CI 1.00-1.17) but not in current smokers (AOR 1.02; 95% CI 0.94-1.11). Additionally, it significantly increased the risk of ACRN among never smokers (AOR 1.17; 95% CI 1.01-1.35) and tended to increase the risk of ACRN among former smokers (AOR 1.26; 95% CI 0.99-1.61). Moreover, the risk of CRN increased with increasing frequency and duration of passive smoking in never and former smokers.
Conclusions: Passive smoking was an independent risk factor for CRN in never and former smokers. Never and former smokers who are highly exposed to passive smoke as well as current smokers should be given priority for colonoscopy.
Keywords: colorectal neoplasia; passive smoking; smoking status.
© 2017 Journal of Gastroenterology and Hepatology Foundation and John Wiley & Sons Australia, Ltd.