Scientific Explanations
A Good Night for Our Brain: The Journey Begins with Side Sleeping
As you close your eyes to start your nightly sleep, a sweet sense of calm surrounds you, allowing you to leave behind the exhaustion of the day. At that moment, it’s not just about physical rest; it’s also an opportunity for your brain to repair itself. Many people believe that waking up in the morning feeling refreshed and clear-headed is a coincidence. However, this clarity comes from an extraordinary night-time cleaning process between your brain cells, called the glymphatic system. Years ago, when we lost an elderly relative to Alzheimer’s disease, it was the first time we deeply realized how crucial sleep quality and position could be in later life. This fascinating brain cleaning process is not only related to how long you sleep but, closely, to how you sleep. Notably, side sleeping makes a vital difference, something that scientists have been carefully studying in recent years.
What Is the Glymphatic System?
Our brain, with all its complexity, works tirelessly like a city and produces waste. The glymphatic system acts as a life-support squad, clearing out this waste by circulating between nerve cells and giving our brain a nightly clean-up. Discovered in 2012 by Nedergaard and colleagues, the glymphatic system gets its name from glial cells and the lymphatic system. Cerebrospinal fluid (CSF) spreads throughout the brain tissue, collecting toxins and metabolic waste that accumulate during the day, and then removes them from the brain through veins.
Some of the most significant wastes are beta-amyloid and tau protein, which can accumulate and cause problems in Alzheimer’s and other neurodegenerative diseases. Multiple studies have shown that these harmful proteins can be reduced with proper glymphatic cleaning. The efficiency of this system depends directly on sleep and, especially, sleep position.
Sleep Positions and Brain Clean-Up
The position you sleep in at night can have a much bigger impact than you think on how you feel in the morning. In a 2015 animal study published in Science Advances, it was reported that the side sleeping position is the most advantageous for brain cleaning. Researchers observed mice sleeping on their backs, stomachs, and sides. The results showed the most effective waste clearance occurred in the side position. Although this study was conducted in mice, it is very likely that similar mechanisms exist in humans.
Sleeping on your back is inadequate for clearing glymphatic waste.
Sleeping face down (on your stomach) can negatively affect breathing and circulation.
Side sleeping increases CSF flow and enables more efficient waste clearance.
We can say with confidence that placing your body in a side position as you rest your forehead on the pillow is a kindness to your brain. Sleeping on the left side is especially often recommended due to its benefits for heart and digestive-circulatory relationships. However, neurology literature does not indicate a clear superiority of right or left side for the glymphatic system; both sides are beneficial.
Scientific Facts That Strengthen the Glymphatic System
The ability of sleep to activate the glymphatic system was clearly shown in a 2013 Nature Medicine article. While glymphatic cleaning levels are markedly low during wakefulness, they can increase up to ninefold during non-REM, deep, slow-wave sleep.
"The brain is the only organ that can truly clean itself only while asleep."
- Maiken Nedergaard, Neuroscientist
In other words: the glymphatic system works 60% more efficiently at night and removes toxic waste with great efficiency. This clean-up plays a decisive role in cognitive processes such as memory, learning, and decision making. It is believed that getting enough and high-quality sleep, especially in the side position, can lower the risk of developing diseases like Alzheimer’s and Parkinson’s (Source).
The Powerful Reflections of Side Sleeping on Our Health
Certain scientific and statistical findings show that side sleeping provides advantages not just for brain health but also for the protection of the heart, respiratory, and digestive systems. About 74% of the world’s population naturally prefers side sleeping in childhood, and this ratio remains high in adults (Sleep Foundation).
Brain Cleansing: Side sleeping allows for easier CSF circulation; waste is cleared more effectively.
Breathing Ease: Those with sleep apnea and snoring benefit from more open airways.
Heart Health: Left side sleeping puts less pressure on the heart and eases circulation.
Gastrointestinal Comfort: For those with reflux or heartburn, it helps prevent acid from moving up the esophagus.
Spine and Muscle Health: With a proper pillow and mattress, lumbar and neck pain may be reduced.
The Practical Effect of Side Sleeping: My Own Experience
To give an example from my own family, my mother struggled with back and neck pain during sleep for years. After changing her sleeping habit from lying on her back to side sleeping, she reported a noticeable increase in strength and vitality. Many of my clients also experienced better glymphatic cleaning and overall comfort with side sleeping. These experiences, combined with scientific data, demonstrate how small but critical changes in our lives can lead to better well-being.
What Happens When the Glymphatic System Is Weak?
If the glymphatic system does not function effectively:
The risk of brain waste accumulation increases
Memory problems may arise
Headaches and decreased cognitive performance may occur
The risk of neurodegenerative diseases such as Alzheimer’s and Parkinson’s rises, especially with aging
In a large-scale study conducted in China in 2021 with 17,000 people, those who slept poorly or with low quality had a 32% higher risk of cognitive decline. Changing your sleep position alone may not work miracles, but by accelerating the brain’s cleaning process, it could be one of our most important defenses during aging.
How to Achieve the Best Side Sleeping Position
Side sleeping is not as easy a habit as it seems—especially if you are used to sleeping on your back or stomach. However, you can develop this skill with a few tips:
Choose a quality pillow. Make sure the head and neck are aligned with the spine.
Place a pillow between your knees to reduce lumbar strain and align your hips.
Support your back with a long pillow or a rolled-up blanket to avoid accidentally rolling onto your back.
Keep your arms close to your body to prevent shoulder and back pain.
Avoid alcohol and heavy meals before sleeping; these can negatively affect glymphatic flow.
Side Sleeping & The Psychological Aspect: Feeling Safe
Let’s take a look from an emotional angle as well. Side sleeping psychologically reinforces our sense of "security." There may be a biological rationale behind the tendency of babies to lie on their sides in their mothers’ arms during developmental stages. Just like the comfort we felt hugging a favorite toy or blanket in childhood, this habit may now bring tranquility and cleansing to our brains as adults.
Gaining a side sleeping habit not only boosts biological cleaning but also helps emotional relaxation, deepening calmness. Especially on days when you feel anxious and have trouble falling asleep, being gentle with yourself and choosing a side position can be a conscious option.
Who Should Be Careful?
No sleeping position is ideal for everyone. Pregnant women are advised to sleep on their sides (especially the left side) for both their own and their baby’s health. Anyone with shoulder pain or recovering from surgery should take their doctor’s advice. For reflux patients, the left side helps prevent stomach acid from going upwards; heart patients may sometimes prefer sleeping on the right or left side. Those with serious health problems should always consult a specialist before changing sleep positions.
Glymphatic Cleaning & Sleep Hygiene: Do They Go Together?
Supporting the glymphatic system throughout sleep is not only about position but also about general sleep hygiene.
Establish regular sleep routines
Ensure the room is dark, cool, and quiet
Limit screen time before bed
Practice relaxation exercises or short meditation
Limit alcohol, smoking, and caffeine
All these habits enhance brain health and optimize the glymphatic system's functionality. Remember: Regulating your sleep in the short term can help preserve your cognitive health in the long term.
The Long-Term Benefits of Side Sleeping
Every night, we can make conscious choices for our well-being as we lay our heads on the pillow. Side sleeping is not just a habit, but a powerful gift to the brain. Healthy aging, delaying forgetfulness, and living a happier life can all be supported by this small but critical habit. Whether you’re young or old, choose side sleeping in your next rest to support your glymphatic system.
If you wake up in the morning feeling light in spirit and clear in mind, remember the power of sleep position. One small step for your health can contribute greatly to your life for years to come.
Small Change, Big Impact
Many of us hesitate to change our habits. However, no matter our age, we should remember that small changes supporting brain health can make a big difference over time. Side sleeping can prepare you for a healthier, more energetic, and clearer future. Before falling asleep, check your position once again—your brain will thank you.
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