*2.5. Data Synthesis*

The studies that met the inclusion criteria have been presented as a narrative synthesis [29,30]. Subsequently, a meta-analysis was conducted, detecting the association between hookah smoking and the risk of obesity, however expressed, using Review Manager 5 (RevMan 5.3. Copenhagen, Denmark) software developed by and for the Cochrane collaboration [31]. A random e ffects model was used to calculate the pooled relative risk and the 95% CI.
