Pediatric Epigenetic Clock
As the field of epigenetic aging has broadened to study the effects of childhood exposures on aging, pediatric epigenetic clocks have been developed. The most prominent childhood clock is the Pediatric-Buccal-Epigenetic clock69 (PedBE) - a 94-CpG buccal epithelial cell clock developed using exclusively pediatric samples (n=1,032, age range: 0.17-19.47 years) and elastic net regression. PedBE’s performance was evaluated in an independent set of 689 buccal samples (age range: 0.01-19.96 years)69 where it had median AE=0.35 years and r=0.98, demonstrating greater accuracy for that age group compared to the pan-tissue Horvath clock69. However, when applied to an independent set of blood samples (n=134), the PedBE clock was not as accurate (median AE =3.26 years) as the Horvath pan-tissue clock (median AE= 0.57 years)69. This performance discrepancy (blood vs. buccal samples) was expected due to the tissue and cell-type specificity of DNAm. DNAm patterns are highly influenced by tissue types as well as by cell type proportions in whole blood.