My mother sleeps for long periods of time, ie: 18 hrs + falling asleep in her chair. Does this seem normal? She is 91 with dementia for 10 yrs. She has worn her rotator cuffs in her shoulders away so she has constant back and shoulder pain. Otherwise healthy as a horse. She gets sundowners and hallucinates at night. Is this something that someone else has seen? Do I continue to let her sleep? Gotta be careful how I wake her up. Will take your head off if you know what I mean.