Sleep Drive: A Brief Introduction

We’ve all heard the term Sex Drive before, right?

To make sure we pass on our genes and keep the old species chugging along, evolution built in a pretty strong biological urge to have sex.

In general, we call strong, biologically-based urges like these drives. Hunger and thirst are similar drives, for example.

But something most of us don’t realize is that we also have a drive for sleep. Like consuming calories and making babies, getting some sleep each night is pretty important to our survival, so our bodies come prepackaged with a mechanism to make that happen.

That mechanism is Sleep Drive, and understanding how it works is key to improving your sleep.

Before we dive into the nitty gritties, let me explain where we’re going with all this…

What you’ll get out of this article

I wrote this article because I want to pull back the curtain on this mysterious but powerful force that affects all of us every day of our lives. Despite not getting much popular press over the years, Sleep Drive has been the cornerstone of effective treatment for insomnia and sleep problems for decades now. And there’s no reason more people shouldn’t know a bit about it.

I have two goals for this article:

  1. I want to describe a fascinating and powerful aspect of our sleep that almost no one knows about. Sleep Drive is one of only two truly impactful factors in how well we sleep (Arousal is the other, btw). If you can understand how it works on a fundamental level, you’ll never think about sleep the same way again.
  2. I want to help you harness this powerful drive to dramatically improve the quality of your sleep (and therefore everything else in your life, since all of it depends to some degree on quality sleep). For example, you’ll learn why if you’re struggling with your sleep, there’s a really good chance you should be spending LESS time in bed not more.

Intrigued? Skeptical? Good. Let’s dive in.

What is Sleep Drive?

Sleep Drive is a measure of a person’s biological need for sleep.

When we first wake up in the morning, our Sleep Drive is very low. It gradually increases as the day progresses and then quickly diminishes as soon as we fall asleep. The implication of this is that the longer you’re awake, the stronger your drive (or need) for sleep.

Adenosine: The Active Ingredient in Sleep

Let’s get a little nerdy for a second:

The strength of our Sleep Drive depends on the accumulation of a chemical in the brain called adenosine.

Like most chemicals in the body, adenosine serves many functions. But one of the most important is that it regulates Sleep Drive, and by extension, the feeling of sleepiness and ability to fall asleep.

When we wake up after a good night’s sleep, our brain adenosine levels are very low.

Over the course of the day, however, they gradually build up until they cross a threshold, at which point we begin to feel sleepy and then are able to fall asleep.

Please Note: I use the term “sleepy” deliberately here because it is technically distinct from the more common term “tired.”

You’d be tired after running a marathon but not necessarily sleepy. When it comes to sleep, it’s best to reserve the term sleepy for a state of being close to falling asleep, while tired is more general and has more to do with exhaustion, stress, fatigue, etc.

You can always tell, by the way, when you’re actually sleepy and not just tired by watching out for the two signs true of sleepiness: The Head Nod and Heavy Eyelids. Other phenomena like yawning, low energy, and feelings of relaxation are often associated with sleepiness but aren’t necessarily reliable indicators of being truly sleep.

All of this means that if you want to feel sleepy, fall asleep quickly, and stay asleep, you need to accumulate lots of adenosine in your brain over the course of the day.

So, how do I accumulate more adenosine?

The short answer: Be awake for longer.

Here’s the slightly longer answer:

Simply by virtue of being awake and going about your day, adenosine and therefore Sleep Drive will build up. However, you can increase the overall amount of adenosine that’s accumulated by increasing your level of physical activity throughout the day, especially through exercise.

If you remember back to high school biology, the body combines glucose and oxygen to form ATP as our muscles’ primary fuel source. What you probably didn’t learn (or forgot) is that as a by-product of the ATP-creation process, your body releases adenosine. Which means that the more work you make your muscles do, the more ATP and therefore adenosine is going to be created.

In terms of sleep, this means that if we want to build up more Sleep Drive, we have to A) Be awake longer, and B) Move/Exercise more.

That’s cool. But how will this help me sleep better?

Here’s the idea in a nutshell:

  • The longer we’re awake the more adenosine builds up in our brain and the stronger our Sleep Drive is.
  • The stronger out Sleep Drive, the more sleepy we feel.
  • The more sleepy we feel, the greater the odds of us falling and staying asleep.
  • Therefore, if we want to fall asleep faster and stay asleep, we need to be awake more.

Obviously, this leads to a bit of a paradox: If we want to sleep better we have to… stay awake longer?

Exactly, here’s how it works…

The Paradox of Sleep Restriction

The term sounds a little horrifying at first blush, but Sleep Restriction is actually a good sleeper’s best friend.

By intentionally staying awake longer (i.e. restricting our sleep), we can increase our Sleep Drive and therefore our chances of falling asleep quickly and staying asleep throughout the night.

Suppose on a normal day you wake up at 7:00 am and get in bed at 11:00 pm. That means you have 16 hours of Sleep Drive built up when you get into bed. Now this may or may not be enough Sleep Drive to result in your feeling sleepy and being ready to fall asleep. And if it’s not, you’re going to stay awake in bed.

But suppose you had to work late and didn’t get home until midnight and then didn’t get into bed until 1:00? Now you’ve had 18 hours to build up Sleep Drive and your odds of exceeding the sleepiness threshold are much higher. Which means you’re more likely to fall asleep quickly after getting into bed, and to sleep throughout the night.

Sleep Restriction is simply a way of intentionally doing what happened here by accident.

By deliberately staying awake longer and restricting your time in bed, to allow more sleep drive to build up. Which means that when you do finally get into bed, you’re that much sleepier.

By trading off a little bit of sleep quantity, we can dramatically improve our sleep quality.

Before we go any further, a couple of clarifications about Sleep Restriction:

  1. Typically, only mild amounts of Sleep Restriction are necessary to increase sleep drive. If you generally need seven hours of sleep each night, Sleep Restriction might involve cutting your time in bed down to 6.5 or 6 hours. Most guidelines recommend not going below 5.5 hours per night.
  2. Sleep Restriction is not something you need to do indefinitely. Sleep Restriction is most useful as a way to temporarily increase your Sleep Drive in order to more effectively get rid of old, unhelpful sleep habits and build new more effective ones. Once your sleep’s back on track, you can stop restricting.

It sounds paradoxical, but most people who are having trouble with their sleep should probably try a mild course of sleep restriction.

Simply cut back on the amount of time you spend in bed by a half an hour each night for a week and see what happens.

While you can restrict your sleep on either end (i.e. going to be later or waking up earlier), it’s often a good idea for most people to start with staying up a little later in the evenings.

If you do this consistently for a week or so, you should start to notice that you are more sleepy when you get into bed and possibly that you wake up less often in the middle of the night and are able to fall back asleep more quickly.

Remember, the whole idea behind Sleep Restriction is to temporarily trade of some sleep quantity for increased sleep quality. You’re going to feel more sleepy-that means it’s working! Once you’re consistently falling asleep quickly and sleeping through the night, add back the hours you removed.

Disclaimer: If you’re struggling significantly with sleep issues, including insomnia, talk to your medical provider and consider Cognitive Behavioral Therapy for Insomnia, which is the consensus treatment of choice for insomnia and similar sleep problems.

Wrapping Up

Sleep Drive is the body’s natural need for sleep which gets stronger the longer we’re awake. One of the simplest and most powerful tools for improving your sleep quality is to try some mild Sleep Restriction. By going to bed slightly later and waking up slightly earlier, you increase your Sleep Drive and consequently your chances of falling asleep quickly and sleeping soundly through the night.