Squares indicate study-specific OR; the size of the box is proportional to the weight of the study; horizontal lines indicate 95% confidence interval (CI); diamond indicates summary OR with its corresponding 95% CI. A: homozygote; B: heterozygote; C: dominant model; D: recessive model; E: additive model. To access the data, click or select the words “Appendix 1.” This will initiate the download of a compressed (pdf) archive that contains the file.