It is also a recognised side-effect of long-term donepezil use (Aricept), the drug that's often used to lessen the effect of Alzheimer's. If it's really bad it might be worth stopping the drug. I give my mother a good many other things too (an Albion chelated magnesium suppliment, a good set of combined B's, garlic, a probiotic and ginger for better digestion and many more I think could be doing something but will never know for sure), so I am considering this route myself. Most of the things I get her (from the USA as it's cheaper) have shown double-blind trial results at least good as donepezil, which the verdict is still out on really, if not a little better. None of them cure it of course.
The drug-related leaning problem is called Pisa syndrome, and when it comes for Mum (so far it can come and go) it can be a real pain for us, as Mum is still really active, despite having the disease for well over 10 years now (since the 90's), and possibly as much as 20 years. She is relatively easy to manage though (though she wasn't at all for a period), and just wants to be out and about walking around all day, which I do with her. She doesn't make much sense any more, but her body's held up really well, and she is happy if the world around her is. Constant and interesting excercise (which needs 1 on 1 care) and the best nutrition humanly possible is the best way to tackle Alz I've found. The disease eats up everything and leaves their brains deficient in many areas, vitamins, minerals etc, which is why I suppliment so much.
As usual with diseases try and keep away from sugars, which tend to feed the disease. Best used as treats in the old-fashioned way. Cake isn't great for the elderly anyway. Sugar is taken via fruit anyway, and apples are particularly good: 1 a day at least. Caffein is the quickest hit to the brain, and should be daily, along with plenty of water - a good mineral water ideally if it's known as being bad where you are. Never, ever dehydrate. I go for at least 6-a-day plus supp's to make sure Mum is nutritionally at least okay. She needs patience at the table, as she often gets up and seems to lose interest, when in reality she'll eat it all and more besides! These days I let her start on chopped up dinner, and take just over if she doesn't make it to the end.
Basically, treat them as much like royalty as you possibly can.