The Reason You Wake Up Feeling Groggy

By Azzy Aslam

Habits, Routines, & Behaviours

14 Dec, 2020

Why Do I Wake Up Feeling Groggy?

Do you feel groggy some mornings when you wake up?  Does it happen after an afternoon snooze too?

There is a very straightforward explanation why you feel groggy after sleeping : Sleep Cycles

I learned this when I was reading some books on sleep. The best best book to date is Matthew Walker’s Why We Sleep. Lots of information about what goes on in our brains when we sleep and also when we are awake particularly if we haven’t slept well or don’t get enough sleep.

Anyhow, back to sleep cycles.


Sleep Cycles

You have a rhythm to your sleep which follows a cycle. The sleep cycle last for an average of 90 minutes. As with many things the timing will varying from person to person. Some may have 83 minute sleep cycles and others may be 94 minutes. And there is nothing to say each sleep cycle will be exactly the same number of minutes, but it will be close to your average.

So, every 90 minutes or so you go from one sleep cyle to the next. Lots of things happen during each sleep cycle but for now I’ll focus just on the overall sleep cycles.

Each of us have a number of cyles we sleep through each night (or the long sleep in a 24 hour period). The minimum number is 4 sleep cycles. Most of us will have 4 – 6 sleeps cycles during the night, which gives you 6 – 9 hours of sleep.

The ideal time to wake up is at the end of a sleep cycle. You would do this naturally if you didn’t have an alarm clock, went to sleep when you are tired, or didn’t have to get up for work or other things you want to, or have to do.

I am sure you can see where this is heading!

When you wake up at the end of a sleep cycle and assuming you have had your 4-6 cycles you will wake up naturally and there’s a good chance you will also feel rested. It’s when you wake up part way through our sleep cycle which makes you feel groggy. Because during the sleep cycle you body and your brain is going through a bunch of processes, which vary from sleep cycle to sleep cycle. When you wake up part way through the cycle you interrupt the sequence of activities. It’s doubly worse if you haven’t got through 4 cycles during the night sleep.

It’s the interruption to the activities your brain and body is going through which causes the grogginess! It’s like putting you clothes in a washing machine.

The wash has a number of cycles the clothes will go through. Wetting the clothes, adding detergent, the wash itself, rinsing to clear the detergent, spinning to remove the water before you can put them out to dry. Imagine if you stopped the wash during one of the cycles…the clothes won’t be ready for drying and you’ll be somewhat stressed!

Getting through to the end of the sleep cycle is important to avoid the feeling of groggy. But what about snoozing?


Feeling Groggy After A Nap

Much the same applies for afternoon naps. But a few things to note which will help you make the most of a nap if you you need  one.

It takes anything between 20-40 minutes to kick in the sleep cycle.  Again, everyone is different and you may fall into the sleep cycle in 20 minutes (or so) or it may take you over 40 minutes. Either way the longer your nap becomes the more likely you have entererd into a full sleep cycle. Which means when you have entered into the full sleep cycle and wake  up, say an hour, into your nap, you will wake up feeling groggy.

The best thing you can do is restrict the amount of time you snooze to between 20-30 minutes otherwise you will enter your full sleep cycle. If you do go over these times you may as well go through to the full 90 minutes or so, to avoid feeling groggy when you wake up.


Final Notes

You may have noticed the sleep cycles don’t add up to the commonly stated thing about having 8 hours of sleep. It’s your sleep cycles which determing how much sleep you need in terms of time and it’s closer to 6, 7.5, or 9 hours rather than 8 hours. If you are trying to work out what time to go to sleep then use these numbers to set your alarm clock rather than 8 hours.

How much sleep you need will vary through your life and also from day to day, depending on the activities and stress levels you go through each day. Your body, and your brain, will tell you when you should be heading to sleep. But in our brightly lit world we ignore these signs and most of the time go to bed much later then our body and brain needs. At the other end of the day, we force ourselves to get up – usually much sooner than we need.

As Matthew Walker says, sleep really is our super power.

But we don’t use it well.

Sleep well!


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