My Older Brother, Age 76, Spends Much Of The Day

my older brother, age 76, spends much of the day talking to himself or eating and watching TV
he pays little attention to his wife ; who says to him she feels like a captive maid
he is really not aware of how his behaviors or lack of them impacts his wife and others around him
should we be worried...
might this be an indication of early onset dementia..or something else...

thank you