My mother is starting to have this problem too. I talked to the doctor this week and she ordered a "swollow test". I understand this is another part of the body that wears out/fails. That is what i know, at least so far.
When I worked there were two swollowing studies one can be done at bedside by a dietician to see if there is a problem and the other is done in a x-ray dept-you would want to see if there is a problem or if she just does not want to eat it is very common to have swollowing problems and can be worked out.