Akl et al. BMC Public Health 2011, 11:244 http://www.biomedcentral.com/1471-2458/11/244 Page 7 of 12 Figure 3 Waterpipe use among school students. South Asia region We identified studies conducted only in Pakistan. University students One study reported 33% current and 53% ever waterpipe smoking (Additional file 3; Part 2). Of these, 31% stu- dents reported sharing waterpipe smoking with others [42]. Both current and ever waterpipe smoking were predominant in males (p < 0.001). Adults One study targeting female adults living on an island reported 41% waterpipe smoking [43]. Another study reported 13% waterpipe smoking [44]. Another study of a nationally representative sample reported 6% cur- rent waterpipe smoking among adults aged 15 and older [45]. In the more representative sample of the two latter studies, the prevalence of cigarette smoking was about 2 times that of waterpipe smoking (Addi- tional file 3; Part 2) [45]. Americas region School students 3 studies targeted 14-18 years old school students with high percentages of Middle Eastern descent (Additional file 3; Part 3) [10,43-45]. These 3 studies reported 12%- 15% current, 27%-36% ever, and 7%-8% regular water- pipe smoking among students of Middle Eastern des- cent. They reported 5%- 8% current, 11%- 21% ever, and 3%-5% regular waterpipe smoking among students of other ethnicities. Current waterpipe smoking was asso- ciated with current cigarette smoking, Arab American ethnicity, grade in school (by grade), and family water- pipe smoking [46,47]. The prevalence of current water- pipe smoking was about 2-6 folds that of current cigarette smoking among Arabs and about half of that of cigarette smoking among non Arabs [11,46-48]. One study targeting middle and high school students of the state of Arizona found 4% current and 6% ever waterpipe smoking [49]. Current waterpipe smoking was associated with grade level, attending a charter school, Asian American and white ethnicities (compared with American Indian or Alaska Native), and male sex [49]. University students 1 study found 10% current, and 41% ever waterpipe smoking. The prevalence of current waterpipe smoking was about half that of current smoking (Additional file 3; Part 3) [50].