Opium use and oral cancer in Iran: A systematic review and meta-analysis

Background: Oral cancer remains a global health burden with persistent low survival rates. While alcohol and tobacco are established risk factors, emerging evidence highlights opium use as a potential carcinogen. This review investigates the association between opium consumption and oral cancer development. Methods: Adhering to PRISMA guidelines, a comprehensive search of Web of Science, Embase, PubMed, and Scopus (inception to February 2025) identified observational studies. Odds ratios were computed utilizing a random-effects model. Heterogeneity, sensitivity, publication bias, and study quality (JBI/GRADE frameworks) were assessed. Results: Six studies (5 case-control, 1 cohort; total sample = 64,412) from Iran were included. Meta-analysis revealed a significant association between opium use and oral cancer (pooled OR = 1.85, 95% CI:1.24–2.57; P = .002), with substantial heterogeneity ( I ²=78.03%). Sensitivity analysis confirmed robustness, and no publication bias was detected (Egger test P = .51). Conclusion: Opium consumption is associated with a nearly 2-fold increased risk of oral cancer, reinforcing its classification as a Group 1 carcinogen. Findings underscore the need for public health interventions in opium-endemic regions, including education, cessation programs, and oral cancer screening integration. The global diversification of research is critical to validate these associations in diverse populations. This study emphasizes multidisciplinary collaboration to mitigate opium-related carcinogenesis.