Epigenetic Clocks

This document describes the generation of epigenetic clocks and immune cell counts from DNA methylation data from participants of the National Longitudinal Study of Adolescent to Adult Health (Add Health). It provides detailed definitions, computation methods, data descriptions, and guidance for interpretation to ensure consistent and reproducible use of these measures. The content here complements existing Add Health documentation on Wave V biospecimen collection and methylation data processing by focusing specifically on several established measures of epigenetic aging.