Fig. 1

The S allele frequency of 21 Caucasian populations and three Asian populations among controls. The center of a box and the horizontal line (logarithm) indicate the prevalence and the 95% confidence interval (CI) in each study, with the areas of the boxes representing the weight of each study. The summary ORs of Caucasians and Asians based on the random effects model are 42.5% (95% CI = 40.8–44.2) and 76.8% (95% CI = 73.9–79.7), respectively. The summary OR is shown by the dotted vertical line. Statistical heterogeneity between studies among Caucasians and Asians were assessed as Q = 43.7, p = 0.002 and Q = 2.60, p = 0.27), respectively, by Cochran’s Q test