Alzheimer's disease is no stranger in the news cycle. The latest headlines are dedicated to a new study on how the brain keeps itself clean, a process which scientists have long suspected to be involved in the disease. This is Healthcare Triage News. [Intro music plays]

To the research! [triumphant music] A new study published in the journal Science examines brain activity during sleep that may relate to removal of molecular markers implicated in Alzheimer's disease. We've known for a long time that people afflicted with Alzheimer's often have trouble sleeping, and we have evidence suggesting that individuals with sleep issues are more likely to develop Alzheimer's.

For example, a 2018 study published in JAMA Neurology found that in individuals aged 70 or older who reported excessive daytime sleepiness, specialized brain scans indicated greater accumulation of amyloid beta, a molecular mark of Alzheimer's, when compared to their less sleepy counterparts.

It's been difficult to understand the direction of the relationship between sleep and Alzheimer's: does poor sleep contribute to disease development, or does the disease cause poor sleep? The JAMA study, which assessed sleep at baseline and then measured amyloid beta buildup in the two years following, lends support to the former: that poor sleep precedes the disease.

Of course, this doesn't prove anything, but it's an important clue. We also have evidence that sleep, particularly deep sleep, is a time during which the brain "cleans house" by flushing out molecular waste, including the kind associated with Alzheimer's. So, the running hypothesis is that poor sleep stymies the brain's ability to clean out molecular villains, whose buildup will eventually lead to neurodegenerative disease.

A couple background items before we move on to the current studies findings. First, the brain and spinal cord are bathed in a fluid appropriately named cerebrospinal fluid or CSF. This fluid has a few jobs in the central nervous system, including what appears to be cleanup duty. Also, your brain produces different waves of electrical activity when you are awake versus asleep. And those waves further differentiate between the various stages of sleep.

Understanding the connection between these two things could be important to understanding the role of sleep in the development of Alzheimer's. So the current study used neural imaging techniques to examine the brain's habit of sleep sweeping, if you will, and how it relates to neuronal activity and blood flow in the brain during sleep.

They saw regular pulses of CSF, immediately following distinct waves of electrical activity. And this coincided with a temporary decrease in blood flow, which could be allowing more room for the CSF to flow through and clean up. Some of the news stories include an excellent image of this process. If you're interested, links down below.

The electrical activity consisted of slow weaves which characterize deep sleep. The consistent pattern of CSF washing through right after the wave of electrical activity, led the authors to suggest that deep sleep electrical waves trigger the process for pickup and removal of waste products in the brain. If this is true, fragmented sleep, or insufficient time spent in deep sleep would disrupt this process, potentially contributing to neurodegenerative disease.

Thus, all of the excitement is due to the idea that this might be the mechanism behind the sleep and Alzheimer's link, not the cure or the key to prevention of Alzheimer's, mind you. As one of the authors noted in an interview, Alzheimer's probably has more than one cause. Sleep may turn out to be a big contributor. But there are many factors at play. 

And of course, there's still work to do. This study offers excellent insight on sleep in the brain, but it only had 11 subjects and none of them have Alzheimer's. That's right. Even though the onslaught of news headlines made claims like, "To decrease Alzheimer's risk, quality of sleep matters," this study did not directly examine Alzheimer's disease.

But flashy news headlines aside, this study may provide a strong step forward in science's quest to understand a devastating neurodegenerative disorder.

Hey, did you enjoy this episode? Always helps if you like and subscribe down below. You might also enjoy this podcast. We spent talking to Liana Apostolova, an expert in Alzheimer's disease. You can also support the show by going to patreon.com/healthcaretriage, where you, along with our research associate, Joe Sevits, and our Surgeon Admiral Sam, can support the show and make it bigger and better.