What Is Deep Sleep, and How Much of It Do You Really Need?
We all know sleep is important, but how do we know if we’re getting enough?
I frequently ask myself this question because I’m notorious for not sleeping enough. It takes me an hour or so to actually fall asleep, and when I do pass out it’s only for a few (blissful) hours. I tend to over-caffeinate in the mornings and use that fuel to power through the day. When I get home I start the process all over again. Working in the sleep space has made me hyper-aware of just how poor my sleep habits really are.
I recently purchased a new sleep app that monitors your sleep activity as well as your sleep environment. After the first night, I got an interesting result:
I only got two hours of deep sleep.
Sleep is arguably one of the most important things we do for our bodies. Healthy sleep has tons of physical and mental benefits, while sleep deficiency is linked to an increased risk of heart disease, kidney disease, high blood pressure, diabetes, and stroke.
Am I at risk? Is two hours not enough deep sleep? How much deep sleep do you need, really?
Let’s look at some sleep facts, starting at the stages of sleep. What happens when we doze off?
The stages of sleep
According to the National Sleep Foundation, our sleep cycles follow a pattern of alternating rapid eye movement (REM) and non-rapid eye movement (NREM) sleep each night in a cycle that repeats itself about every 90 minutes. The cycle is broken down as follows:
NREM: 75% of the night
- Stage 1: The relaxed state before you nod off for the night. You can be awakened easily here. Twitching is common.
- Stage 2: Onset of deeper sleep, when you start to become disengaged from your surroundings and your body temperature drops.
- Stage 3: The deepest and most restorative sleep. It’s difficult to wake someone during this stage. People who are awakened during deep sleep do not adjust immediately and feel groggy or disoriented.
REM: 25% of the night
- After deep sleep, we slip back into stage 2 before entering REM sleep. We spend almost 50% of our total sleep time in stage 2, about 20% in REM, and the remaining 30% in other stages.
Why is deep sleep important?
Deep sleep is an important part of our nightly sleep cycle, in which our bodies repair themselves and build up energy for the next day. It’s where the release of growth hormones occurs in children and young adults, aiding the body’s maturation process. Deep sleep is also when tissue repair occurs, and when your body detoxifies itself. (Fun fact: According to the American Sleep Association, deep sleep is associated with some sleep disorders, like sleepwalking.)
Here’s what the Sleep Association has to say about deep sleep: “Many of the body’s cells also show increased production and reduced breakdown of proteins during deep sleep. Since proteins are the building blocks needed for cell growth and for repair of damage from factors like stress and ultraviolet rays, deep sleep may truly be ‘beauty sleep.’
Activity in parts of the brain that control emotions, decision-making processes, and social interactions is drastically reduced during deep sleep, suggesting that this type of sleep may help people maintain optimal emotional and social functioning while they are awake.”
How much deep sleep do you need?
As we get older we spend less time in deep sleep. Why? One thought is because deep sleep is where growth hormones are released—it makes sense that we spend less time there as we age.
The time we do spend in deep sleep is important in helping repair our bodies and gather energy for the next day. Who doesn’t like feeling rejuvenated after great sleep?
Can you get too much deep sleep?
While it’s certainly possible that you’re not getting enough, you can never get too much deep sleep. So if you’re freaking out about your sleep tracker telling you got 4.5 hours of deep sleep last night, don’t worry. (In fact, you shouldn’t let your sleep tracker allow you to lose sleep.)
“There’s no real way to get too much deep sleep,” Michael Grandner, MD, director of the Sleep and Health Research Program at the University of Arizona in Tucson, tells Fitbit. “Your body has its own natural drive for it, so once you meet that, the need will dissipate and you’ll just start going into REM and light sleep.”
Can a mattress help you achieve deep sleep?
Since we have to pass through several stages of sleep uninterrupted before we reach deep sleep, it’s crucial that nothing disturbs this cycle. One of the most common disruptors of healthy sleep is an old, uncomfortable or ill-fitting mattress.
If you’re wondering how to increase deep sleep, you can start with a mattress that offers support for optimal spinal alignment, while providing relief at key pressure points. That way, even if you change position during sleep, you’re unlikely to be woken by an irritating sleep surface.
The mattress that will afford you the best night’s sleep is the one that best matches your sleep style and preferences. If you’re a back sleeper, for example, you may prefer memory foam, which offers contouring support where you need it most. If you tend to sleep hot, then you’ll stay coolest on innerspring. Latex offers robust, consistent support along with responsive pressure relief and a cool sleep surface. Sleeping on a latex mattress is often described as feeling “weightless” or “uplifting”—it holds you aloft without letting you sink too much. What’s more, latex mattresses are highly durable, so they will last for many years without losing their shape. All this makes latex a favorite among industry experts.
What a sleep tracker taught me about deep sleep
Was I crazy to infer that I needed more deep sleep? Not really. After all, who doesn’t like feeling rejuvenated after great sleep? But with the understanding that I’ll never be 15 again, I’ve learned that I don’t need more than two hours of deep sleep each night.
The next time you pick up your sleep tracker to review your latest sleep statistics, fear not! You’re probably right on track. Some sleep trackers are limited in how much they can really analyze from our sleep.
(Read more about the curious effect that sleep trackers have on sleep.)