If you haven’t heard about the groundbreaking study on Alzheimer’s from the University of California, Berkeley, prepare to be shocked. The study found a connection between disrupted NREM sleep and a buildup of beta-amyloid proteins, which are believed to be linked to Alzheimer’s. The finding implies that poor quality of sleep could be one of the contributing factors to Alzheimer’s.
Here’s another piece of the excitement: we KNOW a fair amount about sleep, so we aren’t entering uncharted territory. We know that as we age, we spend less time in REM sleep, which is why many older adults sleep less soundly at night and often nap during the day. There is no direct correlation between Alzheimer’s and fatigue or between Alzheimer’s and a lack of sleep, but the study’s findings suggest that there could be a potential correlation between Alzheimer’s and the quality of sleep we get. Many scientists would love for sleep to mitigate Alzheimer’s risk because we already know methods to increase sleep quality. But before we all rejoice, let’s take a moment to be good scientists and assess the study’s full range of implications.
What We Already Know
Before we jump into the Berkeley study, let’s do a quick review. We know that there is a significant correlation between individuals with Alzheimer’s and the number of what we call “plaques and tangles” in the brain. Plaques and tangles are the names given to amyloid plaques and neurofibrillary tangles.
That’s great, you might be thinking, and very unhelpful. What are those?
They’re misfolded proteins that can build up inside the brain. They often appear in areas like the hippocampus, where memories are stored. Plaques are made up of beta-amyloid proteins (β-amyloid), and we think they may be a factor in breaking down neural connections between memories and other neural functions. They could also be a by-product of Alzheimer’s and unrelated to the cause.
We know there are two main types of sleep: REM and NREM (non-REM). REM, or Rapid Eye Movement, is the stage most often associated with dreaming. Infants spend a lot of time in REM sleep, leading many scientists to believe it assists in early brain development. NREM sleep, on the other hand, is broken into three types: N1, N2, and N3. We characterize each type by larger and slower brain waves, so N3 waves are the largest and slowest. The N3 stage is most often associated with deep sleep, and the Berkeley study found that sleep disruptions during the N3 stage are associated with beta-amyloid buildup.
Back to the Study
From the Researchers
The team who ran the study, led by Dr. Bryce Mander, noted in their findings that:
“structural equation models revealed that the association between mPFC β-amyloid pathology and impaired hippocampus-dependent memory consolidation was not direct, but instead statistically depended on the intermediary factor of diminished NREM SWA. By linking β-amyloid pathology with impaired NREM SWA, these data implicate sleep disruption as a mechanistic pathway through which β-amyloid pathology may contribute to hippocampus-dependent cognitive decline in the elderly.”
Ok, let’s break that down. The team argues that although they didn’t find a direct association between the buildup of beta-amyloid and Alzheimer’s (remember that we said plaques and tangles are associated with Alzheimer’s but not proven to be a cause), the association was absolutely dependent on the disrupted sleep factor. Because of that, Mander’s team believes that sleep disruption may be one of the mechanisms through which beta-amyloid builds up.
The Berkeley study only measured 26 adults over the course of one night’s sleep in a laboratory — a tiny sample size by any scientific standard. Measuring memory test performance after one night of sleep in a lab also leaves quite a bit of room for skewed results in terms of performance.
The next step of this research will likely be with a much larger sample of people over a more significant time span, where individual results won’t be as prone to skew the overall findings. Mander’s team may also have opened a door into further study on Alzheimer’s and tiredness. Older adults with chronic sleep trouble or those that suffer from both a lack of sleep and Alzheimer’s may be a good next group to study. That said, it’s incredible that after only one night of disrupted sleep, there were significant differences in the buildup of beta-amyloid. It certainly suggests that disrupted sleep may be a hugely influential factor in Alzheimer’s, if not a direct cause.
Does anyone in your family have Alzheimer’s? Do they often tell you their sleep is disrupted? Or do they sleep soundly through the night? Tell us in the comments below!