Sleep Fragmentation and Alzheimer's Risk

I can no longer get a good night's sleep.  My sleep doctor tells me that 7 hours is a good night for me, but getting to 7 hours has proven nearly impossible.  I normally go to bed at 10, but awaken most nights at about 3.  After laying in bed for a while I'll get up and do something for an hour or two, and then go back to bed.  I can usually get enough total sleep time to get to that 7 hour threshold, but, from the standpoint of brain health, is that just as good as sleeping straight through?  I wonder about that a lot.

In July 2018 we posted about why sleep is important in Alzheimer's disease prevention and treatment.  One of the things we noted was that, in deep sleep, the brain cells shrink, causing circulation of cerebrospinal fluid (CSF).  This allows the CSF to deliver the beta amyloid waste to the lymphatic system for removal from the brain.  Accumulation of amyloid plaques in the brain is part of the Alzheimer's disease process, so removal is important.  Varying levels of beta amyloid in the CSF are reflected in varying levels of beta amyloid in the blood.

The sleep cycle is generally about 90 minutes, and the cycle repeats throughout the night.  Deep sleep is only one phase of the cycle, and it begins well into a new cycle.  It is during deep sleep that researchers can measure falling concentrations of beta amyloid in mice and in humans.  And so getting a good night's sleep, with plenty of deep sleep, is important to brain health.

The question that's been on my mind is, if I wake up repeatedly during the night but still get seven hours, is that as good as sleeping seven hours straight?

Probably not.  There was some interesting research reported in the May 2020 issue of the journal Alzheimer's and Dementia that addressed this.  The article was titled "The overnight reduction of amyloid β 1‐42 plasma levels is diminished by the extent of sleep fragmentation, sAPP‐β, and APOE ε4 in psychiatrists on call."  Conclusion: sleep fragmentation diminishes the reduction of beta amyloid levels overnight, so fragmented sleep is probably not as good as uninterrupted sleep.

The research was interesting.  The researchers studied psychiatrists in a hospital in Germany that were on call and thus experienced fairly frequent interruptions in their sleep.  Blood samples were taken from subjects at the beginning and end of their shifts so that change in amyloid levels could be determined.  This was then correlated with sleep interruptions.  There were 17 participants, and they were studied over a total of 90 nights.   Participants kept a log of sleep interruptions, but they also wore instruments to detect motion and corroborate their record.  The subjects were sleeping at the hospital and not at home, and so researchers made an effort to control for varying sources of stress that could confound their results.

So what does this mean for me?  One more thing to worry about.  My neurologist believes that sleep is likely my biggest challenge in dealing with my disease.  Sleep needs vary between individuals, but all of the research I read suggests that I'm not getting enough.  And I wonder if I can even get to an ideal amount of sleep regardless of what I do.

My cognition is to be tested at Harborview in about three weeks.  I was not tested last year, but my subjective sense is that I experienced some unexpected decline then from which I rebounded.  I further sense that I was doing better in the early part of 2020, but I have been declining again.  This goes along with increased trouble with sleep.

But have I really been declining again?  The upcoming testing should provide some clarity.