Why Sleep Is Essential for Health, and How to Optimize It
If I could choose just one thing that would most drastically affect your health and performance, I’d pick sleep. It’s the most important - and sometimes most overlooked - key to wellness, and its effects are far-reaching. I’ll explain why you really do need to sleep well and how to optimize your sleep every single night.
The majority of this information is sourced from Matt Walker, PhD, the prominent sleep researcher from UC Berkley. He has spoken on multiple podcasts, at in-person conferences, and he even has his own eponymous podcast, which I highly recommend if you’d like to dive into any particular topic, such as dreams, sleep and alcohol, sleep and sex, sleep and memory, etc.
Ok, let’s start with the basics: what is sleep? Human sleep is separated into two parts: non-rapid eye movement sleep (NREM) and rapid eye movement sleep (REM). REM sleep is associated with dreaming (although it is possible to dream during other stages), and is characterized by jerky eye movements, which gives it its name. During REM sleep, the nerves that supply our skeletal muscles become paralyzed so we don’t hurt ourselves while we dream, but the nerves that keep our heart beating, our lungs breathing, and our eyes moving are not. NREM sleep is further divided into four different stages depending on the depth of sleep, with the “deep sleep” being the most important.
Image credit OuraRing.com
Every 90 minutes or so, humans cycle between NREM and REM sleep, creating what we call “sleep architecture.” What changes is the proportion of that cycle that is dedicated to NREM versus REM sleep. Most NREM (or “deep”) sleep occurs during the first part of the night, while most REM sleep (and dreaming) happens towards the end of the night. Unfortunately, this means that if you wake up two hours earlier than normal, you could be losing out on a majority of your REM sleep. Most adults really do need 7-9 hours of sleep per night, and less than 5% of the population needs less than 6 hours of sleep (you know who you are).
Each of the types of sleep is critical, but they seem to have different functions. Deep sleep is thought to be important in storing information long-term, whereas REM sleep uses this information to help us make connections and solve problems.
Sleep has many incredible benefits. Sleep actually helps you lose weight by keeping your hunger hormones in check. Leptin (which keeps you full) decreases 18% and ghrelin (which makes you hungry) increases 28% when we are sleep deprived. Deep sleep is also thought to be protective against Alzheimer’s disease, as one of its functions is to clear out the proteins that build up in our brains. Research is ongoing as to whether stimulating deep sleep through brain stimulation might actually be therapeutic for Alzheimer’s.
Sleep also has benefits for mood, cardiovascular health, athletic performance, learning, information retention, memory storage, and it is the time when many of our vital hormones are released, such as growth hormone and testosterone. Sleep improves literally every system in our bodies.
So how do we get to sleep in the first place? It all has to do with a molecule called adenosine. Adenosine builds up in our bodies the longer we’re awake, usually peaking 12-16 hours after we wake up in the morning, and this causes us to feel sleepy. (Caffeine blocks the effects of adenosine, which is how it keeps us awake.) Overnight, sleep clears the adenosine from our brains, and we wake up refreshed.
Knowing this, there are several ways that we can work with our adenosine and our circadian rhythms to optimize our sleep. The most important piece of advice is to start thinking about sleep first thing in the morning. How you structure you day and the choices you make throughout the day can set you up for a peaceful night, or a restless one.
Seeing light first thing in the morning is a powerful way to set your circadian clock and make it easier to fall asleep that night. Andrew Huberman, Stanford Professor of Neurobiology and Ophthalmology, recommends at least 5-10 minutes of natural sunlight - not through sunglasses or through a window - within 30 minutes of waking. This suppresses the sleepy hormone melatonin (which we’ll get to in a minute) and sets your body’s internal clock to fall asleep in about 16 hours. If you can’t get outside to view sunlight (or if you get up before sunrise), bright overhead lights will help.
The second thing you can do in the morning is to increase your core body temperature. Warmth is a powerful stimulus to wake up. Paradoxically, the best way to do that is to take a COLD shower. The cold will make our body’s thermostat produce heat to warm us up, and we’ll release adrenaline which will make us more alert. Exercising in the morning will also help in much the same way.
If you are a coffee drinker, it is best to delay your caffeine for 60-90 minutes after waking if you can. This is because, as we discussed, caffeine blocks the sleepy molecule adenosine. Letting the adenosine naturally clear out of your system will make the coffee more effective. Drinking coffee first thing in the morning sets you up for a crash about mid-afternoon because the coffee will wear off and the adenosine can come rushing back.
Caffeine also has a half-life of about five hours, which is important to know if you like to have an afternoon cup of coffee. If you drink a cup of coffee at noon, about a quarter of the caffeine will still be in your system at 10 pm, so for most people, it’s best to limit your caffeine to the morning.
In the afternoon (between 1-4 pm) our alertness naturally drops, and it actually has nothing to do with whether or not you have a big lunch. Napping at this time offers many benefits to our brain and bodies. Studies from NASA even showed naps as short as 26 minutes offered a 34% improvement in task performance and more than a 50% increase in overall alertness. The downside is that napping can decrease the sleepy molecule adenosine, so if you struggle with falling asleep at night, it’s best to avoid naps. Also, keep naps to less than 90 minutes to avoid falling into a sleep cycle, which can create a situation of “sleep inertia,” or a sleep hangover, where you feel worse afterwards, rather than better. Finally, avoid napping after 2 pm so you don’t interfere with your nighttime sleep.
In the evening, viewing sunlight at a low solar angle can signal to your body to start winding down for sleep. It’s important to keep artificial lighting as dim as possible after sunset, since bright light – especially overhead light – is such a powerful signal for alertness.
Avoiding alcohol at night is the best thing you can do to improve the quality of your sleep. While it might feel like a drink helps you fall asleep, it actually sedates you - which is not the same as normal sleep - and it destroys your sleep architecture. Alcohol increases the chances you’ll wake up from sleep and stay awake by releasing several stress-related chemicals like cortisol, and it suppresses REM sleep. This can lead to impairment in cognitive brain function and emotional stability, and it increases the chances that you’ll wake up with high levels of anxiety.
Once you’re ready for bed, temperature is the most powerful signal for your body to sleep. Your bedroom should be 1-3 degrees cooler than a normal room. Heat exposure, such as a hot tub or sauna, before bed can also paradoxically cool your core temperature for the same reason that a cold shower wakes you up: your body’s internal thermostat will adjust to help your body cool down.
Okay, now let’s talk about melatonin. Melatonin is a hormone that your body naturally releases, and yes, it does make you sleepy. It’s triggered by darkness, and it tells your body that it’s time to go to sleep. The important part is that while it can affect timing, it doesn’t change the quality of your sleep, and it’s not as effective as you might think. Studies show that melatonin decreases the average time to fall asleep by 3.9 minutes and improves sleep efficiency (which is the time you are in bed versus the time you’re actually sleeping) by just 2.2%. Also, melatonin supplements are used at doses much higher than your body could ever produce. The standard dose is 5 mg, where an appropriate dose might be closer to 0.2-0.5 mg. These huge doses have been shown to cause testicular atrophy in mice. While mice are not humans, the consensus is that melatonin should not be the first-line treatment for insomnia.
So what do you do if you can’t fall asleep? First of all, the clinical definition of insomnia is that it takes you more than 30 minutes to fall asleep, or it takes you more than 30 minutes to get back to sleep after you wake up, and that this is happening consistently at least three nights per week. It’s estimated that 10-15% of people have insomnia. The first-line treatment is something called “cognitive behavioral therapy for insomnia,” or CBTI. The key to CBTI is sleep restriction and emotional support. Most people who have insomnia are understandably afraid of sleeping because sleep has failed them. The goal with sleep restriction is to help them build up more adenosine by staying up later. Then they get up at the normal time, and over time, their sleep efficiency improves. In other words, they’re not laying in bed for hours anymore. And at that point, they can transition back to a normal schedule of sleep.
I hope this helped you cover the basics of sleep, why it’s important, and how to best optimize your sleep. If you dozed off during this very long blog, I guess I’ll call it a win. :)
In good health,
Gina