Passive smoking and risk of head and neck cancer: a systematic review and meta-analysis

Studies on the association between passive smoking and head and neck cancer (HNC) are controversial. This meta-analysis aimed to explore this association. A systematic search of the PubMed, Embase, Web of Science, and Cochrane Library databases was conducted up to July 2024 to identify relevant studies. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using the DerSimonian-Laird random-effects model. Heterogeneity among studies was assessed, and the risk of bias was evaluated. A total of 1036 records were identified, of which 17 studies were included. Passive smoking was significantly associated with an increased risk of HNC overall (OR = 1.70, 95% CI: 1.27-2.28, P < 0.001). The association was particularly strong for oral cancer (OR = 1.85, 95% CI: 1.07-3.17, P = 0.026), oropharyngeal cancer (OR = 2.78, 95% CI: 1.29-5.98, P = 0.009), laryngeal cancer (OR = 1.60, 95% CI: 1.24-2.06, P < 0.001), and hypopharyngeal cancer (OR = 2.60, 95% CI: 1.45-4.66, P = 0.001). No significant association was observed for nasopharyngeal carcinoma (OR = 1.14, 95% CI: 0.78-1.66, P = 0.498). Geographically, the risk was elevated among both Asian and European populations. Passive smoking is associated with an increased risk of HNC, particularly for subtypes such as oral, oropharyngeal, laryngeal, and hypopharyngeal cancers. These findings underscore the importance of mitigating exposure to passive smoking as a public health measure.