Waterpipe smoking and cancer: systematic review and meta-analysis.

Objective Although accumulating evidence suggests harmful effects of waterpipe smoking, there is limited information about its direct association with chronic diseases, notably cancer. We provide an up-to-date systematic review and meta-analysis of the association between waterpipe smoking and cancer. Data sources Systematic search of articles indexed in main biomedical databases: Pubmed, EmBase, Google Scholar and Web of Science, published between 1962 and September 2014. Search keywords included a combination of waterpipe or hookah, sheesha, nargile, hubble-bubble, goza or gaylan, and cancer. Study selection Focus on observational studies (cohort, case-control, cross-sectional) that evaluated the association between waterpipe smoking and cancer. Studies with mixed exposures excluded. Data extraction Two investigators independently extracted data and reached consensus on all items. Data synthesis 13 case-control studies met the inclusion criteria and were considered for meta-analysis. The methodological quality of included studies was assessed using the Newcastle-Ottawa Scale (NOS). Meta-analysis revealed a positive association between waterpipe smoking and lung cancer (OR= 4.58 (2.61 to 8.03); I-2= 44.67%), and oesophageal cancer (OR= 3.63 (1.39 to 9.44); I-2 = 94.49%). The majority of studies had a NOS score of 5-6 or 7, indicating 'fair' or 'good' quality, respectively. Conclusions Our findings support a positive association between waterpipe smoking and cancer risk. However, high-quality studies with standardised exposure measurements are needed to clarify the contribution of waterpipe smoking to chronic diseases. More investments in initiatives for surveillance, intervention and regulatory policy for waterpipe smoking are urgently warranted.