Evidence of Passive Smoking as a Risk Factor of High-Grade Squamous Intraepithelial Lesion: A Case-Control Study

This study aims to evaluate the association between passive smoking and high-grade squamous intraepithelial lesion (HSIL) at the sample of Chinese women. We conducted a case-control study to analyze the effect of passive smoking on the incidence that patients diagnosed with HSIL. The participants had undergone cervical cancer screening by cytology and human papillomavirus (HPV) co-testing within a year before the study. Multiple logistic regression was used to explore the effect and interactive effect of risk factors on HSIL. The odds ratio (OR) and 95% confidence interval (CI) were calculated. Passive smokers were 1.57 times (95% CI 1.05-2.35) higher than non-smokers to occur HSIL. The medium of the combined smoking index divided patients into low and high exposure, with the ORs of 1.64 (95%CI 1.02-2.64) and 1.71 (95%CI 1.06-2.77) relative to non-smokers, respectively. The combined smokers in the high exposure group experienced the most considerable risk of HSIL (OR= 4.67; 95%CI 1.17-18.70). The OR of HPV positive passive smoker relative to that of HPV negative non-smokers was 5.28 (95%CI 2.25-14.52;). Passive smokers who reported adolescent exposure history was 4.04 times (95%CI 1.44-11.37) more at risk of the disease than non-smokers. This study supported that passive smoking was a significant independent risk factor on the occurrence of HSIL and showed a positive correlated dose-response relationship. HPV infection interacting with passive smoking led to an even higher risk of the disease. Adolescent exposure to passive smoking persistent for more than 20 years would also increase the risk of HSIL.