> It may be indicative of a health issue
Now you write:
> No study I've seen seems to suggest there's any problem with sleeping more up to something like 12 hrs/night I think
So he said it may be an indication of an issue, and you write that it may not be unhealthy to sleep a lot. Those are two different things.
As for your claim: A quick search returns many hits related to issues caused by sleeping more than ~9 hours. I have not reviewed them (I spent 1 minute on this) so can't say if the studies well performed. Example:
https://www.ncbi.nlm.nih.gov/pubmed/19473367 "Prolonged sleep duration (night-time sleep and daytime napping) may be associated with an increased risk of dementia."
But saying that no study would even suggest there would be a problem seems strange considering I found a bunch of them in a minute. Maybe you have done a deeper review of the studies and concluded that they are invalid, or?
I read a few studies when i started bodybuilding and that seemed to be the consensus
Also undersleep affects cognition to a signifiant degree, iirc it was 40% diminution day one, 60% day 2 on memory tasks (and you have the same health issues as oversleep, perhaps to a higher degree)
> Conclusion: Both short and long duration of sleep are significant predictors of death in prospective population studies. > (...) > Future studies should be designed to answer the question whether sleep duration is a cause or simply a marker of ill-health. https://academic.oup.com/sleep/article/33/5/585/2454478?sear...
> Long sleep was significantly associated with mortality, incident diabetes mellitus, cardiovascular disease, stroke, coronary heart disease, and obesity. https://linkinghub.elsevier.com/retrieve/pii/S1087-0792(17)3...