“…Regarding the study area of the articles; two studies in Ethiopia [ 37 , 38 ], one study in Tanzania [ 39 ],one study in United Arab Emirates [ 40 ], four studies in USA [ 41 – 44 ], three studies in Sweden [ 14 , 45 , 46 ], one study in UK [ 47 ], one study in New Zeeland [ 48 ], and one study in Nepal [ 49 ] were included. As far as the study design of the included articles concerned, we included seven studies case control [ 37 – 39 , 43 , 45 , 46 , 49 ], three cohort [ 14 , 47 , 48 ], two cross sectional [ 40 , 44 ] and two RCT [ 41 , 42 ] studies. Concerning the POP measurement in the included articles, seven studies measured POP objectively [ 37 , 39 , 41 – 43 , 48 , 49 ] and the remaining seven measured subjectively [ 14 , 38 , 40 , 44 – 47 ] (Table 1 ).…”