Emil O W Kirkegaard

With a lot of hormones and metabolic activity that drop with old age the hard question is whether the drop is an adaptation to decay or straight out decay itself. Will replacement cut all-cause mortality? It is hard to tell.

diphenhydramine will do just fine.

Diphenhydramine and some other anticholinergics have been linked to cognitive decline and dementia. Pretty conclusive that risk increases with use for people over 65. Don't make it a habit

I had heard about this...do you have a link to a relevant meta?

I can't find a meta-analysis. Cohort studies by Gray 2015 and Richardson 2018 raised the biggest alarm lately.

link to studies at all?

Would be hard to draw any firm conclusions about diphenhydramine alone from these studies...aside from caution as with any other drug.

Fun fact: a massive acute dose of diphenhydramine (very bad idea, say 500mg+) will obliterate short-term memory for the duration. Someone on the street might mistake the delirious case for an alzheimer's patient...