The association between waterpipe smoking and head and neck squamous cell carcinoma: A multicenter case-control study in Iran.

Although the prevalence of waterpipe smoking is increasing worldwide, evidence on its health hazards, including cancer, is limited. We examined the association between waterpipe smoking and head and neck squamous cell carcinoma (HNSCC) and its subsites. We analyzed data of 918 cases and 3477 controls from the IROPICAN study. Multiple logistic regression models estimated the odds ratios (OR) and 95% confidence intervals (CI). We additionally excluded cigarette smokers, opium users, and nass users to study the association between exclusive waterpipe smoking and HNSCC. The crude OR for ever waterpipe smoking was 1.0 (95% CI: 0.8, 1.3), which decreased to 0.8 (95% CI: 0.6, 1.1) after adjusting for confounding variables. However, we observed statistically non-significant elevated odds of HNSCC (OR: 1.3, 95% CI: 0.9, 1.9), while a significant excess odds of laryngeal cancer (OR: 2.5, 95% CI: 1.0, 5.7) in exclusive waterpipe smokers compared to never tobacco users. Additionally, an especially high OR was observed for laryngeal cancer in exclusive waterpipe smokers with more than 20 years of use (OR: 4.9, 95% CI: 1.7, 14.7). Initiating exclusive waterpipe smoking before the age of 20 was also significantly associated with increased odds of HNSCC (OR: 2.9, 95% CI: 1.3, 6.7) and laryngeal cancer (OR: 9.0, 95% CI: 2.1, 38.2). In conclusion, although no association was found between waterpipe smoking and HNSCC, exclusive waterpipe smoking, particularly at high doses and long duration, seems to lead to an increased risk of HNSCC, especially laryngeal cancer. Larger studies with sufficient power are warranted.