Data sources: MEDLINE, EMBASE and ISI the Web of Science.
Study selection: Articles in any language that assessed the association between water pipe smoking and any health outcome. Included studies were cohort, case-control and cross-sectional. Studies were excluded if they looked at physiological outcomes, non-tobacco pipe use, or didn't differentiate between this and other smoking habits.
Data extraction and synthesis: Data were abstracted independently by two reviewers using a standardised screening guide and GRADE used to evaluate study quality. The I(2) statistic was used to measure heterogeneity. Odds ratios for the effect of pipe smoking on lung, bladder, oesophageal and nasopharyngeal cancer, oral dysplasia, pregnancy outcomes, periodontal disease, hepatitis, respiratory illness and infertility were extracted.
Results: Twenty-three studies were included. Based on the available evidence, waterpipe tobacco smoking was significantly associated with lung cancer, respiratory illness, low birth-weight and periodontal disease. It was not significantly associated with bladder, nasopharyngeal and oesophageal cancers, neither with oral dysplasia or infertility, but the confidence Intervals (CIs) did not exclude important associations. Smoking a waterpipe in groups was not significantly associated with hepatitis C infection. The overall quality of evidence varied from very low to low.
Conclusions: The evidence from very low to low quality studies is that waterpipe tobacco smoking is possibly associated with a number of deleterious health outcomes including lung cancer, respiratory illness, low birth-weight and periodontal disease.