A person with Alzheimer's disease forgets that he fasts in a minute. Whenever he is reminded, it takes him a few minutes to forget again. Can such a person fast?
If a person can fast, let him fast. If he forgets and eats or drinks, people around him do not need to remind, because our Prophet (p.b.u.h.) decrees:
“Whoever forgets he is fasting, and eats or drinks is to complete his fast, as it is Allah who fed him and gave him something to drink.” (Bukhari, Sawm, 26; Muslim, Siyam, 33 (1155))