my bf is bi polar he was diagnosed when he was 27 he's now 57 he has been on lithium and a few yrs ago respiridal we've been together 15 yrs

in the last 6 months he has no energy, sleeps all day, will no longer do any house work is this normal with age??? what else should i expect??? Is there anything I can do to get him more active?? (I try short walks ect, but he says he's to tired)