The end of daylight saving time meant we all turned our clocks forward an hour. And with one less hour of sleep, the day was also greeted with the fervent hitting of snooze buttons and coffee cups held tightly to help combat our sleepiness.
Sleep is something we all do, yet most of us know surprisingly little about what’s actually happening when we close our eyes. So, what should you know about sleep?
Kimberly Fenn is a professor in the Department of Psychology at Michigan State University’s College of Social Science. In honor of Sleep Awareness Week, she breaks down common misconceptions about sleep and shares steps we can take to get better quality sleep.
What is REM and is it the deepest stage of sleep?
Rapid eye movement, or REM, is the phase of sleep characterized by 90-minute cycles, often assumed to be the deepest stage of sleep, but it isn’t. It is certainly the most well-known sleep state, likely because it is the stage in which we primarily dream. It’s the stage in which you have those wild, emotional, bizarre dreams that sort of jump from random events or weird scenarios. They can be highly emotional, highly visual in nature. So, it’s the most famous sleep stage, but it’s also the one that has been discovered most recently in 1953.
When we talk about stages of sleep, the word deep means the neural activity is at its slowest point. If we look at an EEG of the brain in REM sleep, it is indistinguishable from being awake to an untrained eye. Your brain in REM sleep is essentially as active as it is when you’re awake. Interestingly, even though your brain is highly active, your body is completely paralyzed. Your eyes can move and your smaller muscle groups may show some twitching, but the large muscle groups are in a state of atonia or paralysis, which prevents you from acting out your dreams.
If you look at an EEG and see big, high amplitude, slow waves, that’s what we would consider a deeper stage of sleep. The deepest stage of sleep is called NREM Stage 3 which is called slow-wave sleep. In this stage, your respiration and heart rate are slowed and your whole body is relaxed.
Your body prioritizes slow wave sleep early in the night. It’s like when you’re hungry, you crave protein or carbohydrates — food that is more nutritious than starting with dessert. Sleep is the same way. The longer you have been awake, you build up a need for sleep. The sleep that is most critical is the deeper stages of sleep; so, early in the night, your sleep is dominated by slow-wave activity. For an eight-hour sleep window, the first three to four hours are largely dominated by this deepest stage, and then REM sleep dominates the hours before waking.
What does research suggest about the impact of alcohol on sleep?
In some ways, alcohol is a tool for sleep — it can help you fall asleep. Adenosine is a chemical in your cells that promotes sleep. Caffeine is an adenosine antagonist that blocks the action of adenosine, which is why so many of us drink coffee in the morning. But alcohol is the opposite. It primarily impacts the GABA system, but it also increases the levels of adenosine in the brain, which makes you sleepier. It also gives you stronger slow-wave sleep early in the night so, initially, you do sleep better.
The problem comes later at night. Alcohol suppresses melatonin production, and it suppresses REM sleep. So, when your body tries normally to cycle into REM, it can’t and, instead, you wake up more frequently. After a heavy night of drinking, there’s much more fragmented sleep with more frequent awakenings. People consistently report less restorative sleep. Alcohol also can increase snoring during the night and increase incidence and severity of sleep apnea.
So, you end up with a tradeoff: You might fall asleep faster, but you have a much more disrupted night of sleep.
Why might someone still feel tired after eight hours of sleep?
We typically think that if you’ve gotten eight hours of sleep, you’ve done your sleeping job. But not all sleep is the same. If you’re sleeping in a nonoptimal environment, like it’s too loud or too warm, your body is not going to get restorative sleep. It might hover on those lighter stages if you’re repeatedly waking up because of environmental factors.
The other thing is that a lot of people have undiagnosed sleep disorders. People typically know if they have insomnia because you’re awake, but obstructive sleep apnea, or OSA, is different. Many Americans have it and don’t know. A recent report estimates that 80% of cases of OSA remain undiagnosed. Patients with undiagnosed OSA report being in bed for eight hours but may still be sleepy during the day.
With obstructive sleep apnea, your airway closes. This is most likely to affect slow-wave sleep because it’s the deepest stage when your muscles are the most relaxed. The tissues in our neck relax and that closes the airway. So, most of the time, without realizing it, people with obstructive sleep apnea stop breathing hundreds of times a night just for a fraction of a second. This typically results in a greater proportion of lighter stages of sleep. They end up hovering in stage two sleep because every time their body relaxes and starts to enter slow-wave sleep, they stop breathing and come back up. This has profound effects on their daily lives. They will feel excessively tired during the day, and the reduction of oxygen during the night and frequent awakenings also have serious cardiovascular consequences.
It’s important to know that even if you have been asleep for eight hours, it doesn’t mean you’re getting quality sleep. If you’re frequently experiencing excessive daytime sleepiness even after a full night in bed, something is happening while you’re sleeping to disrupt the quality of it.
What are practical steps for people to improve their sleep?
There’s no substitute for good sleep. You can skip sleep and drink a bunch of Red Bull, but you’re not going to do as well. At some point, you’re going to crash. Sleep is so important to your well-being that it’s worth taking measures to improve your sleep.
Step one is to evaluate your sleeping environment. Comfort is important to sleep. People will spend $80,000 on a car but only $100 on a mattress they spend eight hours on every night. There are a lot of bad mattresses out there. Some mattresses are too firm, so your arm goes to sleep if you sleep on your side. Others are too soft, which can lead to muscle pain in various parts of the body. The temperature and ambient noise matter too. These things make a difference in how much deep, restorative sleep you get.
Step two is to prioritize your sleep. We are a very motivated society. People work multiple jobs; students often balance studying and working. The end of the day is often the only free time you get, so it is so easy to stay up too late. One thing that can help is to set an alarm for your bedtime, not just your wake time. Set it as a reminder that this is when you start your bedtime routine. It’s hard to do, but it makes a real difference the next day.
Finally, the third step is to see your doctor if you’re consistently waking up unrefreshed or are sleepy during the day despite adequate time in bed. Something may be disrupting your sleep that you can’t feel or fix on your own.
Fenn’s Sleep and Learning Lab investigates the acquisition and consolidation of complex skills and episodic memory. Learn more about their work here.
