Nowadays, there are so many things that keep us from getting enough sleep. You might be working late, watching too many episodes on Netflix, or getting sucked into your phone – and before you know it, it's 2 a.m.
While it might not always seem like a big deal, these habits can lead to sleep deprivation, which is a real problem. Sleep is one of the most important factors in living a healthy lifestyle. But why does your body need so much rest? And how does it affect you when you don’t get enough sleep? What’s considered “enough” sleep, anyway? We’re diving into all this and more below.
The Science of Sleep
Before we talk about what lack of sleep does to you, let’s talk about the science of sleep.
Your body follows an internal schedule for going to sleep and waking up, called your circadian rhythm. Most people fall asleep at approximately the same time each night and wake up around the same time each morning thanks to their circadian rhythm. Several factors control your circadian rhythm.
A chemical called adenosine is responsible for making you feel tired as the day comes to an end. If you have a healthy sleep pattern, your body breaks down adenosine while you sleep and then you wake up feeling energized.
Sunlight and darkness also play a role in your circadian rhythm. Your body is programmed to feel tired when you are in complete darkness and vice versa. Your brain releases melatonin in the dark — melatonin is a hormone that triggers restful sleep. Meanwhile, light exposure first thing in the morning helps to wake up your brain, helping your brain and body mobilize for the day.
In today’s world, many factors can disturb your circadian rhythm and affect your quality of sleep.
Blue light emitted from computer and phone screens is known to cause poor sleep quality, especially right before bedtime. Caffeine (particularly late in the day) also can interrupt healthy sleeping patterns. And these are just two of the everyday habits stacked against high-quality sleep.
The Stages of Sleep
After you drift off to sleep, you begin a cycle of four different sleep stages throughout the night.
The first three stages of sleep are referred to as “NREM sleep” or non-rapid eye movement sleep. The fourth stage of sleep is “REM sleep,” which stands for rapid eye movement sleep.
You can cycle through these sleep stages multiple times per night.
NREM Stage 1
Sleep Stage 1 occurs right as you are falling asleep. Your transition from wakefulness to sleep slows down certain functions. Most people have some level of awareness during this stage. You aren’t fully asleep, but you’re also not fully awake. For a nap, you’ll want to stay in this light phase of sleep. As you transition into deep sleep, you may experience “hypnagogic hallucinations” and hypnic jerks (you know the feeling).
During Stage 1, the following happens:
- Your brain activity slows
- Your heartbeat slows
- You have fewer and slower eye movements
- Your muscles begin to relax
- Some muscles may twitch
- Your breathing slows
Normally, Stage 1 occurs for about 10 minutes. Next…
NREM Stage 2
Sleep Stage 2 takes up around 50% of your total sleeping hours. This is the stage where you are in “real sleep” and become totally unaware of your surroundings. Your body begins to prepare for the most restful stage of sleep, NREM Stage 3.
During Stage 2, you experience the following:
- You lose awareness
- Your body temperature drops
- Your breathing falls into a rhythm
- Your heart rate becomes steady
- Your eye movements stop
Stage 2 lasts for around twenty minutes per cycle. Your brain has begun to process the information it stored throughout your day.
NREM Stage 3
Sleep Stage 3 is the most restful and important stage of sleep. During this time, you will not easily wake up from noises in your environment and your body is fully relaxed. You often experience lower blood pressure and breathing rates. This is the stage that your brain begins to repair itself, store memories, and process information.
Stage 4 is REM sleep, the sleep stage where dreaming occurs. As your imagination takes over, you experience higher levels of brain activity. Your brain begins to fully process emotions and regulate the storage of emotional memories during REM sleep. As the name suggests, you often have rapid eye movement during this stage.
Your first REM phase hits ~90 minutes in and lasts ~10 minutes, but gets longer in subsequent cycles. Adults typically need four or five REM cycles per night to feel fully rested.
The Importance of Getting Enough Sleep
What happens if you don’t get enough sleep? Well, unfortunately the consequences can be devastating to both your physical and mental health.
While you’re sleeping, your brain uses that opportunity to basically get rid of data that it doesn’t need, and clears out protein and hormonal waste as well. A 2019 study found that cerebrospinal fluid, which circulates throughout the brain and spinal cord, increases in volume during sleep, so that it can wash away junk that has accumulated during the time you’re awake. This removal process operates on a circadian schedule; it's tied to when we sleep and wake up. The accumulation of these waste products is associated with neurodegenerative illnesses like Alzheimer's, so over time, sleep deprivation may impair your neural connections by clogging them up with waste.
Besides cleaning, the brain also needs sleep to replenish itself.
As we experience rapid eye movement and dreaming in our deepest stages of sleep, the brain is physically restored. The brain uses the time you’re sleeping to repair any damage it has sustained during the day, restore metabolic stores, trim useless synapses, reinforce specific connections and overall makes the brain more energy efficient. And physically, a lot of recovery happens in non-REM sleep — that’s when your body builds bone and muscle, regenerates tissue and strengthens the immune system.
While we slumber, the brain is doing some pretty serious DIY — and when it's sleep-deprived, it can't repair itself and therefore can't function at peak efficiency.
Suffice it to say, proper sleep habits are more important than ever. Finding time to sleep can be difficult, but the health of your brain is quite literally on the line.
So, How Much Sleep Do We Really Need?
“Sleep is vital for mental function: alertness, memory consolidation, mood regulation, and physical health,” says Phyllis C. Zee, MD, PhD, director of the Sleep Disorders Center in Chicago.
The amount of sleep you need to stay healthy, alert, and active depends on your age. However, according to the Sleep Institute, you should be getting about seven to eight hours of sleep each and every night.
Using more than 300 studies, a panel of experts determined how much sleep a person needs based on their age:
- Newborns (0 to 3 months): 14 to 17 hours of sleep
- Infants (4 to 11 months): 12 to 15 hours of sleep
- Toddlers (1 to 2 years): 11 to 14 hours of sleep
- Preschoolers (3 to 5 years): 10 to 13 hours of sleep
- School-aged children (6 to 13 years): 9 to 11 hours of sleep
- Teenagers (14 to 17 years): 8 to 10 hours of sleep
- Young adults (18 to 25 years): 7 to 9 hours of sleep
- Adults (26 to 64 years): 7 to 9 hours of sleep
- Older adults (65 years or older): 7 to 8 hours of sleep
Before You Go…
Reaching deeper stages of sleep is equally as important as getting enough sleep. Quality and quantity both matter when it comes to resting well. But sometimes, no matter what you do, you just can’t swing the 7-8 hours of recommended sleep. Our favorite alternative? Daily naps. Specifically the kind where you wake up feeling totally refreshed and energized.
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