Exposure to second-hand smoke and breast cancer risk in non-smoking women: a comprehensive systematic review and meta-analysis.

Through the use of an innovative method to identify original publications, we conducted a meta-analysis of all epidemiological studies evaluating the association between second-hand smoke (SHS) exposure and breast cancer risk among female non-smokers published in English up to October 2022. Pooled relative risks (RR) were obtained through the use of random-effects models. Dose-response relationships were derived using log-linear functions. Out of 73 identified eligible studies, 63 original articles were included in the meta-analysis. The pooled RR for breast cancer for overall exposure to SHS was 1.24 (95% confidence interval, CI, 1.15-1.34, number of articles, n = 52). Regarding the setting of exposure, RRs were 1.17 (95% CI 1.08-1.27, n = 37) for SHS exposure at home, 1.03 (95% CI 0.98-1.08, n = 15) at the workplace, 1.24 (95% CI 1.11-1.37, n = 16) at home or workplace, and 1.45 (95% CI 1.16-1.80, n = 13) for non-specified settings. The risk of breast cancer increased linearly with higher duration (RR 1.29; 95% CI 1.04-1.59 for 40 years of SHS exposure, n = 12), intensity (RR 1.38; 95% CI 1.14-1.67 for 20 cigarettes of SHS exposure per day, n = 6), and pack-years (RR 1.50; 95% CI 0.92-2.45 for 40 SHS pack-years, n = 6) of SHS exposure. This meta-analysis shows a statistically significant excess risk of breast cancer in women exposed to SHS.

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.

Dose-risk relationships between cigarette smoking and cervical cancer: a systematic review and meta-analysis.

OBJECTIVE: Cervical cancer (CC) is the fourth most frequent cancer worldwide. Cigarette smoking has been shown to influence CC risk in conjunction with human papillomavirus (HPV) infection. The aim of this study is to provide the most accurate and updated estimate of this association and its dose-response relationship. METHODS: Using an innovative approach for the identification of original publications, we conducted a systematic review and meta-analysis of studies published up to January 2021. Random effects models were used to provide pooled relative risks (RRs) of CC for smoking status. Dose-response relationships were evaluated using one-stage random effects models with linear or restricted cubic splines models. RESULTS: We included 109 studies providing a pooled RR of invasive CC and preinvasive lesions, respectively, of 1.70 [95% confidence interval (CI), 1.53-1.88] and 2.11 (95% CI, 1.85-2.39) for current versus never smokers, and, respectively, 1.13 (95% CI, 1.02-1.24) and 1.29 (95% CI, 1.15-1.46) for former versus never smokers. Considering HPV does not alter the positive association or its magnitude. Risks of CC sharply increased with few cigarettes (for 10 cigarettes/day, RR = 1.72; 95% CI, 1.34-2.20 for invasive CC and RR = 2.13; 95% CI, 1.86-2.44 for precancerous lesions). The risk of CC increased with pack-years and smoking duration and decreased linearly with time since quitting, reaching that of never smokers about 15 years after quitting. CONCLUSION: This comprehensive review and meta-analysis confirmed the association of smoking with CC, independently from HPV infection. Such association rose sharply with smoking intensity and decreased after smoking cessation.

The role of smoking in COVID-19 progression: a comprehensive meta-analysis.

The association between current smoking and coronavirus disease 2019 (COVID-19) progression remains uncertain. We aim to provide up-to-date evidence of the role of cigarette smoking in COVID-19 hospitalisation, severity and mortality. On 23 February 2022 we conducted an umbrella review and a traditional systematic review via PubMed/Medline and Web of Science. We used random-effects meta-analyses to derive pooled odds ratios of COVID-19 outcomes for smokers in cohorts of severe acute respiratory syndrome coronavirus 2 infected individuals or COVID-19 patients. We followed the Meta-analysis of Observational Studies in Epidemiology reporting guidelines. PROSPERO: CRD42020207003. 320 publications were included. The pooled odds ratio for current versus never or nonsmokers was 1.08 (95% CI 0.98-1.19; 37 studies) for hospitalisation, 1.34 (95% CI 1.22-1.48; 124 studies) for severity and 1.32 (95% CI 1.20-1.45; 119 studies) for mortality. Estimates for former versus never-smokers were 1.16 (95% CI 1.03-1.31; 22 studies), 1.41 (95% CI: 1.25-1.59; 44 studies) and 1.46 (95% CI 1.31-1.62; 44 studies), respectively. Estimates for ever- versus never-smokers were 1.16 (95% CI 1.05-1.27; 33 studies), 1.44 (95% CI 1.31-1.58; 110 studies) and 1.39 (95% CI 1.29-1.50; 109 studies), respectively. We found a 30-50% excess risk of COVID-19 progression for current and former smokers compared with never-smokers. Preventing serious COVID-19 outcomes, including death, seems the newest compelling argument against smoking.