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How Does Napping Affect Our Sleep?

We all feel a little sleepy from time to time.

01/03/2017 8:33 AM AEDT

Hands up who loves a good nap?

Aside from the fact that a mid-afternoon kip is sometimes all you need to keep chugging along with your day, naps are more and more being considered a performance enhancer. But are they only doing you good?

Sometimes you'll wake and feel more alert than ever -- whereas longer naps may leave you feeling groggy. And according to sleep specialist Rosemary Clancy, your nap time can actually eat into your sleep time later.

Understanding our 'sleep drive'

When it comes to regulating sleep, there are two main processes to get your head around: sleep/wake homeostasis and the circadian system. One is a steady state of alertness, the other is an increasing pressure to nod off.

First, to your homeostatic drive. When we have been awake for a long period of time, sleep/wake homeostastis tells us that a need for sleep is building.

"If you were to draw a wave of the 10-12 hours during the day that you have been awake and active, that is your sleep-drive build up," Clancy, clinical sleep psychologist from the Sydney Sleep Centre, told The Huffington Post Australia.

It's pretty straightforward: the longer you are awake, the higher the sleep pressure will become. Sleep onset then reduces this pressure and the propensity to wake. And so the process is restorative.

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Still following?

Linked to this is our internal circadian system that regulates the timing of periods of sleepiness and wakefulness throughout the day.

"Our brain likes to have a defined day and night structure. If you are getting up at the same time each morning -- and getting some early sunlight, which is important for your sleep onset -- you are effectively resetting your circadian biological clock," Clancy said.

The circadian system dips and rises, with an adult's strongest sleep drive generally occurring between two o'clock and four o'clock in the morning and between one o'clock and one-thirty in the afternoon.

What does this have to do with napping?

Quite a lot, actually. These processes are inherently linked. For with every hour, your homeostatic sleep drive is strengthening. And with every nap, it is weakening.

"Your brain will only give you a certain number of hours of sleep and no more," Clancy said. "A long nap in the afternoon can actually weaken your homeostatic drive."

Let's set the scene. It's 2pm and and you're feeling sleepy. You had a terrible sleep last night. It's time to nap.

"If you have been active for about 6 hours of the day, from 7am to 2pm, that might be enough build up -- or enough urgency -- to go into a deep sleep. And then you brain won't want to wake up. If you have an hour's nap, you are probably dissipating the pressure to sleep later," Clancy said.

Expect that you will probably have a later sleep onset that night.

"This doesn't happen for everyone, but for a lot of us, a weakened homeostatic drive can actually keep us up."

And this can be a slippery slope.

"If you brain is getting used to being sleepy at 2pm and having a nap, that association is already built in and will get stronger.

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Make sure your alarm is set.

So, how should we nap?

Before we go any further, we're not disputing naps. There's a whole range of academia promoting their benefits.

"Naps can be a powerful refresher. They can improve your energy levels and your attention span," Clancy. "People have positive connotations of naps and this can only be a good thing. By all means, do it."

What is important to note is the length of your nap -- and your expectations around it.

"Keep your nap to around 20 minutes and set an alarm. If you reach up to 30 minutes, you are going be at risk of entering a deep sleep and it will be harder for your brain to wake up," Clancy said.

"Aside from that, it all depends on how it is impacting our lifestyle or circumstance. If you are going out that night and don't want to feel sleepy until the early hours of the morning, you can afford a longer nap."

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