The end prob is the sleep difficulty. This has been helping me, I believe. I'd love to hear how this works for others. I'm going into a period of intense work, so I might drop out of sight for a bit. I think the central mechanism behind this are normal cyrcadian melatonin and body temperature rythms are disrupted.
Body temperature appears to be link very closely to sleep rythms.
I recently posted an article from Science News to sci.life-extension about immune system impairment and sleep deprivation. I don't have the citation anymore, or I would repost it. The details of study indicated that sleep restriction resulted in a measurable decline in certain certain types of white blood cell counts that were associated with immune system function. I believe that Brian also found similiar evidence from Medline when he did a search on the subject. I would say that the sleep restriction under CR is probably acceptable, since we can demonstrate improved immune system response from CR and increased life span.