“…Twenty-nine published papers were included (Abdala et al, 2003; Altaf et al, 2007; Azim et al, 2000; Azim et al, 2001; Azim et al, 2004; Azim et al, 2006; Baqi et al, 1998; Beyrer et al, 2004; Carey et al, 2006; Chen et al, 2005; de Carvalho et al, 1996; Dowe et al, 2001; El Ghazzawi et al, 1995; Frost et al, 2007; Go et al, 2006; Karapetyan et al, 2002; Kurbanov et al, 2003; Liu et al, 2006; Ostrovskii et al, 1999; Panda et al, 2002; Panda et al, 2007; Panda et al, 1997; Panda et al, 1998; Peak et al, 1995; Rhodes et al, 2006; Platt et al, 2007; Ruan et al, 2004; Rumi et al, 2000; Wai et al, 1996). Two papers (Azim et al, 2004 and Peak et al, 1995) were serial cross-sectional studies involving data from multiple years; these papers were thus listed as two and four separate studies, respectively.…”