When predicting ‘biological age’, always consider whether regression to the mean could be an issue before drawing conclusions. Marije Sluiskes, Jelle Goeman, Marian Beekman, Eline Slagboom, Hein Putter and Mar Rodríguez-Girondo posted a PubPeer comment (a postpublication peer review platform) to a recent publication of Daunay et al. 2022 (Aging) which didn't consider this. [...]