Whether people have dementia or not and this describes them then surely they are
selfish
ˈsɛlfɪʃ/Submit
adjective
(of a person, action, or motive) lacking consideration for other people; concerned chiefly with one's own personal profit or pleasure.
"I joined them for selfish reasons"
synonyms: egocentric, egotistic, egotistical, egomaniacal, self-centred, self-regarding, self-absorbed, self-obsessed, self-seeking, self-serving, wrapped up in oneself, inward-looking, introverted, self-loving;
It is just a describing word, and up to the individual to say what they want, like saying someone is aggressive you could still say they were aggressive even if they weren't before,
or what about kind would you say they were kind if they weren't before,