Global DNA (hydroxy)methylation is stable over time under several storage conditions and temperatures.
Helen R GosseltPieter H GriffioenBertrand D van ZelstNatanja OosteromRobert de JongeSandra G HeilPublished in: Epigenetics (2020)
Global DNA methylation and hydroxymethylation stored as blood and DNA can be used for epigenetic studies. The relevance of small differences occuring during storage depend on the expected effect size and research question.