Domestic Burning of Incense and Mosquito Coils on the Risk of Nasopharyngeal Carcinoma: Systematic Review and Meta-Analysis

Objectives To clarify the association between incense and mosquito coils burning and the risk of nasopharyngeal carcinoma (NPC), we performed this systematic review of epidemiological studies. Methods A search of studies published through October 2022 in MEDLINE and EMBASE databases was performed, supplemented by searches of reference lists, recent reviews, and Chinese databases. The quality of the included studies was assessed with special reference to exposure assessment. Random-effect meta-analysis estimated the pooled odds ratios (OR) and 95% confidence interval (CI) whenever applicable. Results One cohort and 12 case-control studies were identified. The cohort study found no association between incense burning and NPC risk. In meta-analysis of six case-control studies with reasonable quality, the pooled OR for incense burning during adulthood was 1.61 (95% CI 1.43–1.81). Five studies assessed association between exposures to incense smoke during childhood and NPC risk, and the pooled OR was 1.22 (95% CI 0.76–1.96) associated with incense burning at birth and was 1.37 (95% CI 1.10–1.71) for exposure at the age of 10 years. The pooled OR for mosquito coils burning during adulthood was 1.30 (95% CI 1.04–1.62). None of the four previous case-control studies found an increased risk of NPC associated with mosquito coils burning during childhood. Conclusions Our findings suggest an increased NPC risk associated with incense burning and mosquito coils. More epidemiological studies with refined exposure assessment are still warranted.