Second-hand smoke exposure and cervical cancer: a systematic review and meta-analysis

Purpose The association between second-hand smoke (SHS) exposure and cervical cancer (CC) risk is still unclear. The aim of this study is to provide an accurate and updated estimate of this association. Methods Through an original methodology to identify original publications, we conducted a systematic review and meta-analysis of all epidemiological studies published up to October 2022 evaluating the association between SHS exposure and CC risk among female non-smokers. Meta-analytic estimates were obtained using random-effects models and dose–response relationships were derived using log-linear functions. Results Out of 25 eligible studies, 21 were included in the meta-analysis, providing a pooled relative risk (RR) of cervical intraepithelial neoplasia (CIN) of grade 2 or higher of 1.52 (95% confidence interval, CI 1.30–1.78, 21 studies) for overall SHS exposure versus non-exposure. When restricting the analysis to invasive CC, the pooled RR was 1.42 (95% CI 1.17–1.71, 13 studies), whereas the pooled RR for CIN was 1.50 (95% CI 1.22–1.84, 6 studies). Analyzing RR by setting or source of SHS exposure resulted in significant associations with CC risk for SHS exposure at home (RR for CIN2+ 1.49, 95% CI 1.21–1.84, 14 studies), in non-specified settings (RR for CIN2+ 1.64, 95% CI 1.20–2.23, 8 studies) and from partner (RR for CIN2+ 1.55, 95% CI 1.25–1.94, 10 studies). The risk of CIN2+ significantly increased linearly with the intensity and pack-years of SHS exposure. Conclusion This comprehensive review and meta-analysis confirmed the association of SHS exposure with CC, further suggesting the need to raise concern about SHS exposure in the population.