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Some discoveries completely change the way we see things, and this one really made me rethink my sleep routine. Did you know that our brain "cleans" itself while we sleep? Without enough quality sleep, we put ourselves at greater risk of cognitive decline. Once you understand how this process works, you might rethink your sleep habits too.
How the Glymphatic System Works
The brain cleanses itself through a complex process that primarily occurs during deep sleep, facilitated by the glymphatic system. This large-scale waste clearance system was first discovered in 2012 by researchers at the University of Rochester Medical Center.
Think of the glymphatic system like a network of tiny drainage pipes in your brain. These pipes, formed by special support cells called "astroglial cells", run alongside blood vessels. Imagine a city with a system of street cleaners that only work at night. During the day, traffic is too heavy, so waste builds up. But at night, when the streets are quieter, these cleaners can sweep through, flushing out the rubbish and keeping everything running smoothly. In the same way, when you're asleep, your brain's "cleaning crew" gets to work, using these tunnels to flush out waste and toxins, helping to keep your brain healthy and functioning properly.
The key mechanisms include:
Cerebrospinal Fluid (CSF) Exchange – Think of CSF as your brain’s built-in cleaning fluid. During deep sleep, it flows through the brain like a dishwasher cycle, washing away the waste that builds up throughout the day.
Interplay Between Blood Vessels and Astrocytes – Imagine your brain’s waste removal system as a kitchen sink. Blood vessels act like the pipes, and special support cells (astrocytes) create spaces around them where CSF mixes with other fluids to flush out the waste—just like water in a sink carrying away food scraps.
Increased Fluid Flow During Sleep – During deep sleep, your brain expands its "drainage system" by about 60%, making it much easier to remove harmful toxins. It's like opening up extra lanes on a motorway at night to clear out traffic jams, keeping everything running smoothly for the next day.
Why Brain "Cleaning" Matters
The glymphatic system plays a vital role in maintaining brain health by clearing metabolic waste and excess proteins. This helps:
Prevent Neurodegeneration – Imagine your brain as a workspace. If clutter piles up, it becomes harder to function efficiently. Toxic proteins like beta-amyloid and tau can build up and contribute to diseases such as Alzheimer’s and Parkinson’s. A well-functioning glymphatic system helps "clean the desk" before problems arise.
Support Cognitive Function – Just like a tidy workspace improves productivity, a well-cleansed brain enhances memory, concentration, and decision-making. When the glymphatic system is disrupted, it can lead to brain fog and difficulty focusing—like trying to work in a messy room.
Distribute Essential Nutrients – The glymphatic system isn’t just about waste removal; it also ensures vital nutrients like glucose, lipids, and amino acids are delivered where they’re needed. Think of it as a delivery service that keeps the brain fuelled and functioning optimally.
Why Deep Sleep is Crucial for Brain Health
The glymphatic system is most active during slow-wave sleep (deep sleep). If deep sleep is compromised, the brain’s ability to clear waste is reduced, leading to the gradual accumulation of potentially harmful substances.
Research indicates that sleep deprivation can weaken the glymphatic function and may contribute to cognitive decline. Chronic lack of sleep is linked to an increased risk of Alzheimer’s, as the brain struggles to clear beta-amyloid plaques. Even a single night of poor sleep can cause a temporary build-up of potentially harmful proteins in the brain.
How to Support Brain Health Through Better Sleep
Habits to improve deep sleep:
Maintain a Consistent Sleep Schedule – Going to bed and waking up at the same time each day helps to regulate your body’s internal clock and supports deep sleep.
Optimise Your Sleep Environment – A cool, dark, and quiet room promotes uninterrupted sleep. Avoid screens and bright lights before bed, and aim to get some sunlight in the day as these both can influence melatonin which helps us to sleep well.
Practice Relaxation Techniques – Meditation, deep breathing, or gentle stretching before bed can help to ease the transition into restful sleep.
Stay Hydrated – Proper hydration supports CSF production. Drink consistently throughout the day, include food with high hydration and soluble fibre to help absorb the fluid you take in.
Limit Alcohol and Caffeine – Both substances may interfere with deep sleep quality. Reducing consumption, particularly before bedtime, can improve sleep efficiency - I find coffee after midday affects me! But you might have different tolerances.
Exercise Regularly – Did you know that moderate aerobic exercise has been shown to improve our glymphatic function and overall sleep quality.
The Role of Exercise in Brain Health
Exercise plays a key role in maintaining a healthy sleep cycle and supporting brain health. A review by Dolezal et al. (2017) found a strong relationship between physical activity and sleep: good sleep enhances physical performance, while regular exercise improves sleep quality. Another study by Chennaoui et al. (2015) suggests that exercise can serve as a non-pharmacological treatment for sleep disorders by promoting deep sleep and glymphatic clearance.
Hydration and Diet for Brain Health
Proper hydration is essential for cerebrospinal fluid circulation. Dehydration can impair the glymphatic system, making it harder to flush out toxins. A diet rich in antioxidants, omega-3 fatty acids, and anti-inflammatory foods supports cognitive function and reduces oxidative stress in the brain.
Sleep and Menopause: A Vital Connection
Sleep disturbances are one of the most common and disruptive symptoms of menopause. Research by Xu & Lang (2014) found that perimenopausal and postmenopausal women experience significantly higher rates of sleep disturbance than premenopausal women. This is largely due to hormonal fluctuations, night sweats, and increased anxiety.
A 2024 review by Maki et al. highlighted the role of oestrogen-sensitive neurons in regulating body temperature, sleep cycles, and mood. Disruptions in these pathways can lead to frequent night-time awakenings, reduced sleep quality, and daytime fatigue.
Poor sleep can worsen mood swings, cognitive difficulties, and overall health risks in midlife women. Research into targeted treatments for menopause-related sleep issues is ongoing, and future developments could provide much-needed relief, but in the meantime, please try to adopt some of the suggestions here as this general health information will also be good to help you sleep well.
The Bigger Picture
This research is relatively new, and scientists are still uncovering the full impact of the glymphatic system on brain health. However, what we do know is compelling—sleep isn’t just about rest; it’s about repair. Prioritising deep sleep could be one of the simplest yet most effective ways to safeguard long-term brain function, especially for women navigating menopause.
So, the next time you think about cutting back on sleep, remember—your brain relies on that downtime to clear out waste. If that’s not a reason to prioritise rest, I don’t know what is.
1. Chennaoui, M., Arnal, P.J., Sauvet, F. and Léger, D., 2015. Sleep and exercise: a reciprocal issue? Sleep Medicine Reviews, 20, pp.59-72
2. Dolezal, B.A., Neufeld, E.V., Boland, D.M., Martin, J.L. and Cooper, C.B., 2017. Interrelationship between sleep and exercise: a systematic review. Advances in Preventive Medicine, 2017(1), p.1364387.
3. Iliff, J.J. and Nedergaard, M., 2013. Is there a cerebral lymphatic system?. Stroke, 44(6_suppl_1), pp.S93-S95.
4. Jessen, N.A., Munk, A.S.F., Lundgaard, I. and Nedergaard, M., 2015. The glymphatic system: a beginner’s guide. Neurochemical Research, 40, pp.2583-2599.
5. Maki, P.M., Panay, N.B., Simon, J.A., 2024. Sleep disturbance associated with the menopause. Menopause, 31(8), pp.724-733.
6. Rasmussen, M.K., Mestre, H. and Nedergaard, M., 2018. The glymphatic pathway in neurological disorders. The Lancet Neurology, 17(11), pp.1016-1024.
7. Rasmussen, M.K., Mestre, H. and Nedergaard, M., 2018. The glymphatic pathway in neurological disorders. The Lancet Neurology, 17(11), pp.1016-1024.
8. Xu, Q., Lang, C.P., 2014. Examining the relationship between subjective sleep disturbance and menopause: a systematic review and meta-analysis. Menopause, 21(12), pp.1301-1318.
Really interesting post - thanks Rachel. I work and earn my living as a writer and illustrator, so my brain has to work overtime all day, mostly to the detriment of exercise. I usually don't remember dreams - is that indicative of anything?