MWB...interesting question to which I do not have a definitive answer.
However, it depends upon what sort of sleep pattern they had before they became "elderly" and I am not so sure that in terms of hours, it remains the same.
O.K they probably sleep less at night, but most elderly have a "kip" during the day that makes up for the nightime decrease.
Oh dear..... pasta calculates late nights on AB....what was it-4am the other night.......so maybe 5 hours at the most...a KIP during the day...a KIP after work.....bloody hell...PLEASE not the care home!!!!