Nevertheless, the forensic aDMPs also showed inter-individual variations in the direction of DNA methylation changes.

These markers displayed larger changes in DNA methylation with age compared to all the aDMPs and less variation among individuals. Twenty-three of the 2821 aDMPs were previously incorporated into forensic age prediction models. Significant variation in the baseline DNA methylation levels between individuals of similar ages as well as inconsistent direction of change with time across individuals were observed for all the aDMPs. A mixed-effects model identified 2821 age-associated differentially methylated CpG positions (aDMPs) with a median rate of change of 0.18% per year, consistent with a 10–15% change during a human lifespan.

The present study investigated epigenome-wide methylation profiles in 64 individuals over two time points, 15 years apart, using the Illumina EPIC850k arrays. DNA methylation, a pivotal epigenetic modification, plays a crucial role in regulating gene expression and is known to undergo dynamic changes with age.