Second-Hand Smoke Linked to 20 Percent Increased Lung Cancer Risk in Never-Smokers: Meta-Analysis Confirms

The researchers note that the highest risk was observed in workplace environments (1.38), followed by a slightly lower risk at home (1.20). They emphasized that prolonged and intense exposure further heightened the likelihood of developing lung cancer.

Lung cancer is the leading cause of cancer-related deaths globally, and research indicates that second-hand smoke exposure is a significant risk factor for lung cancer in individuals who have never smoked. With this in mind, Irene Possenti, Department of Medical Epidemiology, Istituto di Ricerche Farmacologiche Mario Negri IRCCS, Milan, Italy, and colleagues aimed to provide the most precise assessment of the link between SHS exposure and the increased risk of lung cancer in never-smokers.

For this purpose, the researchers conducted a systematic review and meta-analysis of epidemiological studies examining the link between second-hand smoke (SHS) exposure and lung cancer risk in never-smokers. By employing an innovative method to identify original publications, they included all relevant studies published up to May 2023. Pooled relative risks were calculated using random-effects models, and dose-response relationships were analyzed through log-linear functions or cubic splines to better understand the intensity and duration of exposure's impact on lung cancer risk.

The study revealed the following findings:

· 126 eligible studies were identified, with 97 original articles included in the meta-analysis.

· The pooled relative risk for lung cancer due to overall SHS exposure was 1.24 (based on 82 studies).

· Setting-specific relative risks for lung cancer were:

• 1.20 (n=67) for SHS exposure at home.
• 1.38 (n=30) for SHS exposure in the workplace.
• 1.37 (n=28) for SHS exposure in both home and workplace settings.
• 1.27 (n=24) for SHS exposure in nonspecified settings.

· The risk of lung cancer significantly increased with longer duration, higher intensity, and more pack-years of SHS exposure.

"Our meta-analysis offers robust and current evidence highlighting second-hand smoke exposure as a significant risk factor for lung cancer in never-smokers. These findings have crucial public health implications, stressing the importance of raising awareness about the dangers of SHS exposure. It encourages individuals to adopt smoke-free environments, such as smoke-free homes," the researchers wrote.

"Additionally, policymakers are urged to incorporate these findings into the creation, implementation, and enforcement of comprehensive smoke-free policies, particularly in workplaces, to reduce SHS exposure and mitigate the associated health risks," they concluded.

Reference:

Possenti I, Romelli M, Carreras G, et al. Association between second-hand smoke exposure and lung cancer risk in never-smokers: a systematic review and meta-analysis. Eur Respir Rev 2024; 33: 240077 [DOI: 10.1183/16000617.0077-2024].