A recent study from the US has uncovered a relationship between circadian rhythms and the immune regulation of plaques in the brain, a hallmark of Alzheimer’s disease. Alzheimer’s is a neuroinflammatory disease which causes a decline in memory and cognitive function, in addition to speech. These findings allow the molecular mechanisms of Alzheimer’s to be understood in the context of our disrupted circadian rhythms.
Amyloid-beta plaques are observed in the brains of those suspected of having Alzheimer’s. While these are naturally occurring proteins, the abnormal levels that are found in affected brains impact the functioning of cells.What is not clear is how, why or when these plaques form in the brains of those with Alzheimer’s.
The authors of the study found the presence of daily clock correlated with the clearance of these amyloid-beta proteins. When the circadian rhythm was disrupted in the brain, the clearance of these proteins also became disrupted. Importantly, this suggests the disruption of circadian rhythms is a potential mechanism behind Alzheimer’s.
Circadian rhythms are 24-hour cycles that constitute the body’s internal clock. Ever wondered why your body wakes you up at a certain time in the morning without an alarm? That is because many of the systems in our body are synchronised with a master clock in our brain, specifically a group of neurons in the hypothalamus. Our circadian rhythms are closely tied to the light patterns of our environment, which allow the release of hormones that signal sleep, including melatonin, which you may be familiar with. You may have also heard that blue light is detrimental to sleep, and should be restricted before bed as it obstructs the release of melatonin which can disrupt your circadian rhythm.
Why should we care about our circadian rhythms? Well, as hardworking students, or avid partygoers, we find ourselves sacrificing sleep. On the due dates of our assignments, we often run down 11:59pm submission deadlines and reward ourselves with a midnight scroll of our TikTok For You pages. Other nights, when facing a 9am compulsory tutorial, we reluctantly go to bed at 10pm and mute our group chats. Simply put, we often have inconsistent sleep schedules which throw off our circadian rhythms, unaware of the implications this may have on our health.
Returning to the link between circadian rhythms and the clearance of the amyloid-beta proteins, it’s important to note that experiments enhancing their removal haven’t been shown to suppress disease progression. Dr Claire Goldsbury, a University of Sydney Senior Lecturer involved in research into amyloid beta plaques, suggested they “could well be completely irrelevant to the underlying cellular mechanism of disease”.
She questioned whether there may be other circadian-regulation functions responsible for loss of cell function as ”the extracellular accumulation of these peptides in the brain could just be a marker for an underlying intracellular process…. that is dysfunctional in AD [Alzheimer’s Disease].”
Knowing the potential importance of circadian rhythms when it comes to Alzheimer’s, we ought to keep them consistent. And there are a couple of things that we can do. First, it’s important to keep to a sleep routine. Try winding down at the same hour every night and go off your screens for a while. Whether that is by taking a hot shower, or sticking to a nightly skincare routine, your brain benefits from any signals that trigger sleep. Second, seeking sun in the early hours of the day can help calibrate your circadian rhythm. So go out and make use of the morning sun! And third, getting exercise in the morning can also regulate your hormone levels, making it easier for you to fall asleep – not only will this get your endorphins pumping, it will also shift your circadian rhythm to an earlier sleeping time.
Circadian rhythms govern many of our internal processes. As such, learning about it is the first step to understanding why our body behaves the way it does. Particularly, it is fascinating to see how it could explain possible protective mechanisms for neuroinflammatory diseases such as Alzhemier’s. As more research emerges, particularly targeting Alzheimer’s, keep an eye out for new ways to keep your internal clock ticking routinely. If we keep that clock ticking, our future selves might thank us!