Assessing the effect of waterpipe smoking on cancer outcome - a systematic review of current evidence

Background: Waterpipe smoking (WPS) is widely believed to be a safe and hazard-free tobacco habit. However, a number of studies have indicated that exposure to several toxicants and carcinogens through WPS is strongly related to serious health hazards. The current paper presents a narrative review on the effects of WPS on cancer outcome. Methods: The addressed focused question was "Is there an association between waterpipe smoking and cancer outcome?" PubMed, Medline, EMBASE, ISI Web of Science and the Cochrane databases were searched until June 2015 using the key words "Waterpipe", "Hookah", "Narghileh", "Shisha", "Hubbly Bubbly" "cancer" in various combinations. Letters to the Editor, review articles, case-reports and unpublished articles were excluded. Results: A total of 16 studies were included: six on lung cancer, three on oesophageal cancer, two on gastric cancer, two on bladder cancer, and one each on nasopharyngeal, pancreatic and prostate cancers. Our search did not yield any study that evaluated the risk of oral cancer in WPS users. The available evidence showed a significant association of WPS with lung cancer (UOR 6.0, 95% CI 1.78-20.26); however, no association was observed with bladder, nasopharyngeal, pancreatic and prostate cancers. Gastric (OR 3.4, 95% CI 1.7-7.1) and oesophageal cancers (OR 1.85, 95% CI 1.41-2.44) were observed to have weak associations with WPS. Conclusion: Regardless of the limitations, there is sufficient evidence to suggest associations of WPS with cancer, particularly in the lung. Future well-designed studies are required to identify and quantify with confidence all the health effects of this form of smoking.