Comment on “Causal linkage of tobacco smoking with ageing: Mendelian randomization analysis towards telomere attrition and sarcopenia” by Park et al. — The authors reply

[...]please note that the genetic instrument provided for the smoking initiation was ‘not’ weak and showed notable statistical power in our analysis. [...]we believe the current MR analysis was performed with sufficiently powered genetic instruments, although the remaining potential of a false positive bias is present. [...]following the above second point, we clearly noted the limitation of our MR analysis containing overlapping samples in our manuscript with details. ‘In the GWAS of GSCAN data without UK Biobank, only 8 SNPs associated with Smoking Initiation were identified at the significance level of p values < 5E-8. [...]another analysis at the significance level of p values < 5E-6 was also conducted.’ [...]we are not certain about the biological interpretation they suggested, because sarcopenic traits are inter-related.