title: Cancer risk in waterpipe smokers: a meta-analysis.
abstract: OBJECTIVE
  To quantify by meta-analysis the relationship between waterpipe smoking and cancer, including cancer of the head and neck, esophagus, stomach, lung and bladder.
  
  
  METHODS
  We performed a systematic literature search to identify relevant studies, scored their quality, used fixed and random-effect models to estimate summary relative risks (SRR), evaluated heterogeneity and publication bias.
  
  
  RESULTS
  We retrieved information from 28 published reports. Considering only highquality studies, waterpipe smoking was associated with increased risk of head and neck cancer (SRR 2.97; 95 % CI 2.26-3.90), esophageal cancer (1.84; 1.42-2.38) and lung cancer (2.22; 1.24-3.97), with no evidence of heterogeneity or publication bias. Increased risk was also observed for stomach and bladder cancer but based mainly on poor-quality studies. For colorectum, liver and for all sites combined risk estimates were elevated, but there were insufficient reports to perform a meta-analysis.
  
  
  CONCLUSIONS
  Contrary to the perception of the relative safety of waterpipe smoking, this meta-analysis provides quantitative estimates of its association with cancers of the head and neck, esophagus and lung. The scarcity and limited quality of available reports point out the need for larger carefully designed studies in well-defined populations.
authors.affiliation: Department of Global and Public Health, Weill Cornell Medicine-Qatar, Doha, Qatar. ram2026@qatar-med.cornell.edu.
authors.forename: Ravinder
authors.initials: R
authors.lastname: Mamtani
authors.affiliation: Department of Global and Public Health, Weill Cornell Medicine-Qatar, Doha, Qatar.
authors.forename: Sohaila
authors.initials: S
authors.lastname: Cheema
authors.affiliation: Dean's Office, Weill Cornell Medicine-Qatar, Doha, Qatar.
authors.forename: Javaid
authors.initials: J
authors.lastname: Sheikh
authors.affiliation: Smoking Cessation Program, Hamad Medical Corporation, Doha, Qatar.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Al Mulla
authors.affiliation: Department of Surgery, New York Medical College, Valhalla, New York, USA.
authors.forename: Albert
authors.initials: A
authors.lastname: Lowenfels
authors.affiliation: Division of Epidemiology and Biostatistics, European Institute of Oncology, Milan, Italy.
authors.forename: Patrick
authors.initials: P
authors.lastname: Maisonneuve
mesh_terms: D006801:Humans; D009369:Neoplasms / Q000209:etiology*; D012306:Risk; D012907:Smoking / Q000009:adverse effects*; D062789:Tobacco Products / Q000009:adverse effects*; D014867:Water
chemical_list: D014867:Water
keywords: Cancer; Hubble bubble; Meta-analysis; Shisha; Smoking; Waterpipe