The results of subgroup analyses performed according to the potential sources of heterogeneity.

Abbreviations: No. of datasets, Number of datasets (papers); MDS, Myelodysplastic Syndrome; AML, Acute Myeloid Leukemia; Nor A, North America; NOS, Newcastle-Ottawa Scale; Pub. bias, Publication bias; CBC, cannot be calculated; OR, odds ratio; AOR, Adjusted OR; CI, Confidence interval; PB, Population-based; HB, Hospital-based.The results of subgroup analyses performed according to the potential sources of heterogeneity.