PER2 and type 2 diabetes mellitus: It is interesting to note that the variants displaying significant disease associations in individual populations in our study appear to have opposite directions of effect on type 2 diabetes and prostate cancer; that is the minor alleles of the CRY2 and NPAS2 variants that appear to increase the risk of diabetes in one or more of our datasets are associated with a decreased risk of prostate cancer in the study of Zhu et al[23], while the putative diabetes-protective alleles near PER2 and CRY1 appear to confer an increased risk of prostate cancer.