FIG. 2.

Theoretical aging epigenome scenarios. Average DNA methylation and standard error at one CpG site from a single tissue type are shown for a hypothetical study population sampled at three time points (T1= birth, T2 = adolescence, and T3 = middle-age). Possible scenarios include but are not limited to: (A) no age-related methylation, baseline epigenetic drift, (B) no age-related methylation, environmental deflection of epigenetic drift, (C) normal age-related hypomethylation, baseline epigenetic drift, (D) age-related hypomethylation and environmental deflection of epigenetic drift, (E) environmental deflection of age-related hypermethylation, and baseline epigenetic drift, and (F) environmental deflection of both age-related hypermethylation and epigenetic drift. Changes could have occurred gradually over time or suddenly at a specific developmental time point.