My mother is in the early- to mid-stage of Alzheimer's. She is often anxious, because she cannot remember what she needed to do, or if she has done it! This anxiety is the source of her repetitive questions, which exhaust my patience and that of our substitute caregiver.
I found that the most simplified recorder possible really helped with this problem. (www.kindreminder.com). I leave comforting, reassuring messages for Mom, and she plays them over and over again. A typical message might be, "Hi, Mom, you've had a good breakfast and taken all of your medication. Mary is here with you, and I will be back after lunch." The recorder is worn as a pendant and has only one, very big button for playback.
My mother is calmer and more aware of what's going on. Also, there's less tension between us. I hope this can help other families.