Theories on epigenetic aging include roles for stem cell biology and potentially circadian rhythm.

“there are many theories some people think uh stem cell biology plays an important role and that's probably true for many tissues you know certain ways it could measure aspects of stem cells for example how often a stem cell divided and the problem with that inside interpretation is that the epigenetic clocks work beautifully in neurons you know which really don't rejuvenate over the lifespan you know and yes another group thinks that epigenetic clocks might relate to circadian rhythm”