Certainly pop-sci but great on this topic:
https://www.waterstones.com/book/why-we-sleep/matthew-walker...
I'm not as optimistic as you that sleep will be a cure, but I'd be very surprised indeed if sleep quality weren't preventive. (Proving this might be more difficult, though - correlation/causation).
It's almost an argument by process of elimination - why else would literally every living thing with a brain need to spend so much of its time asleep? How is it that we still don't fully know what sleep (as distinct from either rest or unconsciousness) is actually for?
Multiple studies show that night shift work is bad for the brain - and for those with a habit of working nights (probably quite a few of us on HN, from time to time), if a recreational drug made your brain feel as bad as an all-nighter can, that would surely be one you'd put in the "treat with great caution" category, no?
No doubt the glymphatic system (a central part of higher animal physiology which was only discovered in the last 25 years) has a role to play. It may be that, as with cancer, once the degenerative process gets beyond a certain point, it's hard to stop - but I'm hopeful that science will unlock a good deal of understanding around prevention over the next decade or so - even if that's not much more than an approach to sleep hygiene analogous to "eat your 5 fruit and veg a day, don't have too much alcohol or HFCS, and make sure to do a couple of sessions of cardio and a few weights every week".