I’ve held for awhile that the science supporting this conceit is iffy, my feeling has been that at best it provides a way to mitigate some of the accumulated environmental insults of living. The mechanics of how such a thing could work mechanically had been out of reach which seems bizarre for something so systematic. A specific bone to pick was that it wasn’t all exercise (e.g. weight lifting past a certain point lowers lifespans) that was beneficial, just anaerobic exercise (and again, up to a point, after which it becomes harmful again). More importantly, what sense from an energy standpoint does it make to require these high expenditure periods to maintain homeostatic range?
I came across some work this week on correlations between the glymphatic system and disorders of comprehension. It strikes me that what we are really measuring with plaques, tangles, and bodies may really indicate is insufficient glymphatic clearance. Low clearance seems a pretty reasonable jump to accumulation etiologies, including those which note the “traveling” of insults like Ass plaques and Tau tangles. It’s also the mechanic for the contradiction of why these accumulation insults appear in clinical and non-clinical samples equally, senescence lowers homeostatic plasticity of cells. Lowered glymphatic clearance means waste backs up into cells themselves and eventually results in apoptosis. And cellular apoptosis is the major source of accumulation model particles.
Imagine being able to breathe wide open when young, but the sinus passageways close up as you age. This means that senescence makes it more difficult to respond to the metabolic stress of infection, and each cold, flu, etc was that much worse. Why is being obese is so deadly? Lipids clogging the clearance systems would induce the same type of damage as advanced senescence.
The idea of senescence limiting homeostatic plasticity seems like an intriguing bit of consistency in lots of diverging models.