Are You Washing Your Brain Properly at Night?

Jul 6

We all know that sleep is important. We know that a bad night's sleep leaves us feeling tired, irritable and less able to concentrate. But what if one of the most important things your brain does while you sleep is quite literally clean itself?

As a Principal Osteopath, I talk about sleep with patients regularly. Sleep affects pain, inflammation, recovery and how our nervous system responds to the world around us. However, some of the most interesting research into sleep is looking much deeper into the brain itself and a system known as the glymphatic system.

The easiest way I can describe it is this: while you sleep, your brain appears to enter a state that allows fluid to move through its tissues more effectively, helping to clear away some of the metabolic waste products that have accumulated while you have been awake.

So, are you washing your brain properly at night?

What Is Actually Inside Your Brain?

Your brain is not simply a solid mass of nerve cells packed tightly inside your skull.

It contains billions of neurons, supporting glial cells, blood vessels and spaces through which fluid can move. Surrounding the brain and spinal cord is cerebrospinal fluid, or CSF.

CSF is a clear fluid that cushions and protects the brain and spinal cord. It also plays a role in maintaining the chemical environment of the central nervous system and in the movement and clearance of metabolic waste.

The brain is incredibly metabolically active. Even when you are sitting still, your brain is working continuously. Neurons are firing, neurotransmitters are being released and recycled, and cells are using energy.

As with any active biological system, this activity produces waste products.

Among the substances researchers are particularly interested in are beta-amyloid and tau proteins.

Why Are We Talking About Plaques?

Beta-amyloid is a protein fragment produced naturally in the brain. Problems can occur when beta-amyloid accumulates and aggregates, contributing to the formation of amyloid plaques.

Amyloid plaques are strongly associated with Alzheimer's disease, while abnormal tau proteins can form tangles within brain cells. These changes are two of the major pathological features researchers look at when studying Alzheimer's disease.

It is important to be clear that developing Alzheimer's disease is far more complicated than simply “not sleeping enough”. Genetics, ageing, cardiovascular health and many other factors are involved.

However, scientists are increasingly interested in the relationship between sleep, the brain's waste-clearance systems and the accumulation of proteins such as beta-amyloid and tau.

Your Brain's Night-Time Cleaning System

In 2013, researchers published a fascinating study looking at what happened to the brains of mice during sleep.

They found that the extracellular space within the brain increased by approximately 60% during sleep. This appeared to allow greater movement of fluid through the brain tissue and was associated with faster clearance of beta-amyloid.

This waste-clearance pathway has become known as the glymphatic system.

The name comes from its association with glial cells and its lymphatic-like role in clearing waste from the central nervous system.

CSF moves along spaces surrounding blood vessels and exchanges with the fluid between brain cells. This movement appears to help transport soluble proteins and metabolic waste away from brain tissue.

In very simple terms, when we sleep, the brain seems to create a better environment for this fluid exchange and clearance to take place.

It is not quite a pressure washer for your brain, despite how I may have described it to patients in clinic, but “washing the brain” is a surprisingly useful way of visualising what researchers are studying.

Deep Sleep

Not all sleep is the same.

Throughout the night, we move through different stages of sleep, including rapid eye movement, or REM sleep, and non-REM sleep.

Research into the glymphatic system has particularly focused on deep, slow-wave non-REM sleep.

More recent studies have continued to investigate how sleep affects beta-amyloid and tau. A 2025 study found that slow-wave sleep was associated with reductions in CSF concentrations of beta-amyloid and tau, supporting the theory that deep sleep may be particularly important for brain clearance.

The science is still developing and, as with most areas of neuroscience, it is more complicated than the headlines sometimes suggest. There is ongoing debate about exactly how brain clearance changes during sleep and how findings from animal studies translate into humans.

What is becoming increasingly difficult to ignore, however, is the relationship between chronic poor sleep and long-term brain health.

Consistently Poor Sleep

One poor night's sleep is not going to cause dementia.

As a parent, I am extremely grateful for that fact.

My sleep is regularly affected through no choice of my own. Children wake up, people become unwell and sometimes life simply does not allow for eight hours of uninterrupted sleep.

The concern is more about persistent poor sleep and chronically disrupted sleep quality.

Sleep disturbance is associated with cognitive decline and neurodegenerative disease, although the relationship appears to work in both directions. Poor sleep may contribute to changes within the brain, while early neurological changes can themselves disrupt normal sleep patterns.

This means scientists are still trying to establish exactly what is cause and what is effect.

From a practical perspective, however, sleep is one of the areas of our health that we can at least try to influence.

Brain: Now Switch Off

This is something I am increasingly aware of in my own life.

If I watch a highly stimulating television programme in the evening, my sleep quality is affected. I may physically go to bed at the same time, but I do not necessarily feel that my brain has settled.

We often spend the entire day asking our nervous system to perform.

We work. We answer emails. We manage children. We scroll through social media. We deal with noise, decisions, deadlines and constant information.

Then, at 10.30 pm, we turn the television off, put our phone down and expect the brain to immediately switch into deep restorative sleep.

Biologically, it does not always work like that.

The content we consume before bed may be just as relevant as the screen itself. Research around blue light is more nuanced than we once thought, and simply putting a blue-light filter on your phone does not automatically make late-night scrolling sleep friendly.

If the programme you are watching is frightening, emotionally intense or so gripping that you watch “just one more episode”, your brain is still being stimulated.

For me personally, I notice this quite clearly.

Think About Caffeine

Caffeine is another obvious but frequently underestimated factor.

Caffeine works partly by blocking adenosine, a chemical involved in building our natural drive to sleep.

Research has shown that caffeine consumed even six hours before bedtime can significantly disrupt sleep.

That means your 4 pm coffee may still be relevant when you are trying to sleep at 10 pm.

Individual caffeine sensitivity varies considerably, but if you struggle to fall asleep, wake frequently or feel that your sleep is light, it is worth looking at when you consume caffeine rather than simply how much you drink.

Try moving your last caffeinated drink earlier in the day and see whether you notice a difference.

Snacks Before Bed?

Evening eating habits are another area worth considering.

Chocolate can contain caffeine and theobromine, both of which can have stimulating effects. Large meals, very sugary foods and carbohydrate-heavy snacks immediately before bed may also affect some people's sleep through digestion, blood glucose changes or simply making them feel uncomfortable.

This does not mean carbohydrates are “bad” for sleep. The relationship between food and sleep is far more complicated than that.

However, if your evening consists of coffee, chocolate, sugary snacks and stimulating television until the moment you go to bed, it is probably unreasonable to expect your nervous system to instantly become calm and your sleep to be perfect.

Look at the entire evening, rather than searching for one miracle sleep supplement.

Sleep Isn't Always Within Our Control

I am writing this as both an Osteopath and a parent, and I know that getting a perfect night's sleep is not always realistic. My own sleep is often interrupted through no choice of my own and, like many parents, there are periods where good quality sleep simply isn't happening as often as I would like.

There are plenty of other reasons people struggle with sleep too. Pain can make it difficult to get comfortable or cause you to wake when you move. Hormonal changes, stress, shift work, caring responsibilities and health problems can all affect both how long we sleep and the quality of that sleep.

For me, the interesting part of the research into the glymphatic system is that it gives us another reason to look at the things we can influence. I can't always control whether one of my children wakes me in the night, but I can look at whether I've had caffeine late in the afternoon, spent the evening watching something particularly stimulating or been staring at my phone before going straight to bed.

It is worth looking at your own evening routine and being realistic about what you are asking your brain to do. If you have spent the entire day working, thinking and processing information, followed by an evening of television, phones and constant stimulation, going to bed does not necessarily mean your brain is immediately ready for good quality sleep.

Reducing caffeine later in the day, being more aware of evening screen use and giving yourself a little time to wind down before bed are relatively simple changes. A dark, comfortable bedroom and a reasonably consistent sleep routine can also help support better quality sleep.

We often think of sleep as the period where we are doing nothing, but the brain is far from inactive. Memories are being processed, hormones are being regulated and the movement of fluid and waste products within the brain changes while we sleep.

There is still a huge amount to learn about the glymphatic system and its role in long-term neurological health. However, the research gives us a fairly compelling reason to take the quality of our sleep more seriously.

Perhaps “washing your brain” is an oversimplification of an incredibly complex neurological process, but it is certainly a good way to remember why getting a good night's sleep is about far more than simply feeling less tired the next morning.