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

Abstract

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.

Keywords: Cervical cancer; Cervical intraepithelial neoplasia; Dose–response relationship; Meta-analysis; Relative risk; Second-hand smoke.

Fig. 1

Forest plot and pooled relative risk (RR) of cervical intraepithelial neoplasia of grade 2 or higher (CIN2+) for women exposed to second-hand smoke (SHS) compared to non-exposed women, overall and by study design. 95% CI 95% confidence interval, E exposed to SHS, NE non-exposed to SHS

Fig. 2

Relative risk (RR) for the dose–response relationships between second-hand smoke (SHS) exposure intensity and pack-years, and the risk of cervical intraepithelial neoplasia of grade 2 or higher (CIN2+). a Hours per day of SHS exposure (based on four studies). b Cigarettes per day of SHS exposure (based on three studies). c Pack-years of SHS exposure (based on three studies). Bold line: linear regression model; line: 95% confidence interval of the restricted cubic spline or linear model; dotted line: RR for the reference category (non-exposed); bubble: RR for various exposure categories in each study included in the analysis, where the area of the circle is proportional to the precision of the RR (i.e., to the inverse variance)