I am currently reading Why We Sleep as well, and Matthew Walker's research on the topic is really interesting to consider within the larger constellation of approaches to Alzheimer's—particularly in context of the dietary/metabolic angle.

The neural maintenance that occurs during sleep, the body's circadian mechanisms and quality of diet all seem to be highly complementary and ultimately point towards a more holistic and fundamental understanding of the disease (or brain physiology in general). It's been demonstrated pretty comprehensively that quality of diet and timing of eating have a profound effect on how well the body functions as a whole, so the sleep component seems to be an important thread in tying all of these approaches together.