My dad is 91 & has mixed dementia. He goes through phases of sometimes spending 16-18 hours in bed, other phases of less time, but the least amount of time is about 12-13 hours. He just says he’s tired or ‘nice & comfortable.’, had him checked by the doc, said no physical problems at all.
I often think that it’s just easier, he doesn’t have to try & remember where things are, or how to use the tv remote etc & frankly he’s living in a world that he doesn’t recognise or understand in comparison to what he remembers. He can lie in bed, comfortably, with his memories, undisturbed.
I’ve been living with him for some time and we get on well so he has company if he wants it. Obviously I try to encourage him to get up, but all he wants is peace & quiet.
I wouldn’t worry too much
x