SHAFAQNA – The Grand Ayatollah Shobairi Zanjani answered a question about waking up a person for Salaat despite knowing that he/she may get upset.
Question: A person is heavy sleeper, and gets upset when we wake him up for dawn Salaat. Is it allowed to wake him up?
The Grand Ayatollah Shobairi: It is allowed to wake up a person in a way that it is considered beneficial for him, for instance it causes him to get used to waking up at the time of Salaat, or his dignity is preserved in front of others, or to prevent him committing sin by not performing Salaat. It is allowed to wake him/her up even if you assume that by waking him/her up; he/she will perform Salaat.
Source: PERSIAN SHAFAQNA