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Why Sleep Is Important for Brain Health

Why Sleep Matters for Brain Health

A neurologist and sleep medicine specialist explain how sleep impacts our brain health and how to regulate our circadian rhythms for optimal sleep.

It’s estimated that at least 50 million Americans suffer from a sleep disorder. But sleep—both the quantity and quality—is crucial to our brain health. Research has now shown a correlation between sleep disturbances and numerous neurological diseases. These include stroke, cognitive aging, dementia, Parkinson’s disease, and others.

The brain is complex and interconnected. The American Brain Foundation believes finding a cure for one brain disease will help find cures for others. Just as well, the association between sleep and brain health illustrates how one issue can be linked to multiple diseases.

In our recent webinar, Phyllis C. Zee, MD, PhD, Chief of the Division of Sleep Medicine at Northwestern University’s Feinberg School of Medicine, spoke about how sleep and our circadian rhythms play an important role in brain health.

The Role of Sleep and Circadian Rhythms

The “master clock” of the brain, the suprachiasmatic nucleus, controls many systems of the body exhibiting rhythmic activity patterns. Our body systems follow a cycle of rest and activity, synchronized with each other to help the body function. This means sleep is regulated by our bodies at the cellular and molecular level. “Similarly, the circadian rhythm, or these near 24-hour biological rhythms, have been shown to be genetically regulated and they exist in almost every cell of our body,” says Dr. Zee.

It’s a two-way relationship. Our brains and bodies regulate our sleep and circadian rhythms. Equally so, our sleep and circadian rhythms affect our brains and bodies. Sleep disturbances have a broad impact on our health and body functions. They’re also linked to an increased risk for disease, including neurodegenerative disorders like Alzheimer’s and Parkinson’s. Some data indicates that sleep and circadian rhythm dysfunction, such as fragmented sleep or night wakings, may be a risk factor for these types of brain disease.

More specifically, research shows that slow-wave sleep, or deep sleep, decreases with age. A lower amount of deep sleep is associated with an increase in beta amyloid. This is a protein that has been found to accumulate in people with Alzheimer’s. When we get quality sleep, the fluids between neurons are better able to flush out large molecules and prevent toxic buildup through a process called the glymphatic flow. Disrupted sleep could therefore increase the risk for neurodegenerative brain diseases.

Additionally, many people with Parkinson’s disease experience REM sleep behavior disorder (RBD), in which they physically act out their dreams, for years before their diagnosis. In this way, the sleep disorder could be considered a prodromal syndrome, or a sign that may precede Parkinson’s. People with RBD are also more likely to develop cognitive problems or dementia.

How to Improve Sleep and Circadian Rhythms to Preserve Brain Health

This connection between sleep and brain health shows us there is potential to prevent and treat brain diseases by improving sleep and circadian rhythms. Dr Zee asks, “If we can improve sleep and circadian rhythms, can they be these targets for disease modification and some of these age-related changes?”

For example, in one study, researchers used a sound that stimulates slow-wave sleep (acoustic stimulation) to improve deep sleep in older adults. The amount of improvement in slow-wave sleep was directly correlated to an improvement in memory. In another study of people with Parkinson’s, timed light therapy improved daytime sleepiness, sleep quality, daily physical activity levels, and Total Unified Parkinson’s Disease Rating Scale score, which measures the severity and progression of the disease.

For our bodies to function well, our internal rhythm needs to be in sync with our external exposure to light and darkness. The retinas in our eyes have receptors that take in different wavelengths of light, both sunlight and artificial, from across the whole spectrum. Matching your internal clock to that of the sun ensures you get the right types of light at the right times. These daily shifts in light and dark affect our sleep and wake cycles, circadian rhythms, metabolism, and energy levels. Our nutrition—when, what, and how much we eat—also provides information to our master clock.

In this way, our lifestyles can affect our sleep and circadian rhythms. That can mean external factors, like our daily schedule or cycles of light exposure, can negatively impact sleep. But it also means lifestyle changes have the power to positively impact sleep.

To start, Dr. Zee recommends setting a regular sleep-wake schedule that will provide 7 to 8 hours of sleep per night. However, she notes that it’s not only how much you sleep but also when you sleep—that is, staying in rhythm—that is important for brain health. Appropriately timed light exposure and eating, as well as regular exercise and activity levels during the day, will help your body stay in rhythm. Also, reduce or avoid alcohol, as it can disrupt your sleep and suppress REM and slow-wave sleep. This causes a rebound effect that awakens you in the early morning hours.

How Much Sleep Is Enough? How Do You Know You’re Getting Enough?

Regularity is key. We all have a bad night here and there. But if it’s chronic it can have a bigger impact on our health. The general recommendation is 7 to 8 hours for adults, possibly closer to 7 hours for older adults. But there are also individual differences based on our unique bodies and needs.

So how do you know you’re getting enough sleep? Consider how you feel during the day. Are you able to stay awake and attentive and carry out your daily activities? Since we can’t get regular imaging of our brains, these daytime indicators help us gauge how much sleep we need.

Can Medications or Supplements Help You Sleep?

Pharmaceuticals don’t typically provide deep sleep. In other cases, they can induce deep sleep all night long. But they also cause people to wake up feeling “hungover” or more tired. When it comes to deep sleep, more is not better. Timing is important: deep sleep is necessary earlier in the night and dissipates closer to morning.

Melatonin affects the circadian system and promotes sleep by decreasing the arousal, or alerting signal, from the circadian clock. With aging, our natural melatonin levels go down. If you choose to take melatonin, be sure to stick to small doses (between half a milligram to 3 milligrams) unless recommended otherwise by your doctor, as high doses can affect your vascular system.

Some people experience insomnia and feel like they can’t “shut down” their brains. In these cases, imaging shows that even while asleep there is a lot of metabolic activity in the brain, sometimes even more than during the daytime. This may account for the fatigue and decreased attention many of those with insomnia experience. Besides medication, cognitive behavioral therapy (CBT) can help address this issue and decrease that arousal.

What’s the Best Way to Measure Sleep?

Most consumer technology devices, like Fitbits, don’t measure the brain-wave sleep that is an indicator of brain health. However, they can still offer insights about your sleeping patterns and wakefulness during the course of the night. During slow-wave sleep or REM sleep, there are physical changes in your body. These include your heart rate, body temperature, and activity levels. Sensors that monitor those levels can use algorithms to predict when you’re asleep versus when you’re awake, and some newer algorithms can even distinguish light and deep sleep. One advantage to these sensors, as opposed to a formal overnight sleep study, is that they measure every day and can give a sense of your sleep regularity over time.

Is There Anything Wrong With Staying Up Late if You Can Still Get 7 to 8 Hours of Sleep?

As Dr. Zee says, “It’s better to live with your clock than against your clock.” The key is getting the right amount of quality sleep during your individual circadian time. For a “night owl,” living with your clock might translate to a later bedtime and wake time, as your schedule allows. But if you need to accommodate your work or social obligations, the use of light exposure and melatonin can help shift your clock.

Will a Nap Help?

Between 1 and 3 p.m., we may feel a natural “afternoon dip” in energy levels. Taking a nap during this time can refresh us, but it won’t make up for lost nighttime sleep. While we may not sleep for 7 to 8 hours straight every night, consolidated sleep is important. That’s because the extended time allows us to move through sleep cycles. You likely won’t hit all the necessary points in a sleep cycle during a nap.

If you have concerns about your sleep, be sure to speak to your doctor. They can recommend lifestyle changes, medications, or supplements that align with your unique biology and circumstances to help you get quality sleep—and ultimately improve your brain health.