Simulating DNAm drift in >22k blood samples shows stochastic change explains 66–75 % of Horvath clock accuracy, 90 % for Zhang, but 63 % for PhenoAge, implying true aging reflects non-stochastic biology. Male, severe COVID-19 and smoker accelerations stem from these non-random effects.

WGBS of germ-layer tissues and gametes mapped 1,488 hemi-methylated candidate imprint control regions, including 19/25 known. 332 showed near-complete parent-specific methylation and 65 % overlapped CTCF/DNase sites. This draft imprintome opens paths to study imprinting errors in disease.