GDF15 and COVID-19: To verify the stability of the results, we removed rs1227731 and rs888663,we conducted a Mendelian randomization analysis using the same method, we get 4 instrumental variables: rs3746181, rs749451, rs1054565, and rs17725099, none of these SNPs were correlated with COVID-19 or risk factors, and they explained 8.24% of GDF-15 genetic variance (F value = 122.1322), rs1054564 was removed because it was palindromic with intermediate allele frequencies, the secondary analysis results are consistent with our results.