“…9 full-text publications were preliminarily included into this meta-analysis (Ajani et al, 1992;Holly et al, 1996;Guenel et al, 2001;Monarrez-Espino et al, 2002;Stang et al, 2003;Lutz et al, 2005;Schmidt-Pokrzywniak et al, 2009;Schmidt-Pokrzywniak et al, 2010;Behrens et al, 2011). After full-text review of those 9 papers, 2 studies were excluded because they contained overlapping data (Monarrez-Espino et al, 2002;Schmidt-Pokrzywniak et al, 2009), and another studies excluded because they were lack of necessary data (Ajani et al, 1992;Holly et al, 1996). Thus, five case-control studies involving a total of 1199 cases and 6927 controls were finally included into our meta-analysis (Guenel et al, 2001;Stang et al, 2003;Lutz et al, 2005;Schmidt-Pokrzywniak et al, 2010;Behrens et al, 2011).…”