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What the heck are sleep cycles?


Each and every night your body goes through a cycle of different depths (light vs deep) of sleep and what we call REM sleep (the deepest). We don’t stay in one particular depth for long periods, but rather CYCLE through the different levels multiple times throughout the night.

A rough estimate is about 90 minutes to complete a cycle before you start over and begin another one. Here’s something that I’ve been playing with to help with sleep…

Have you noticed that sometimes you’ll wake up and feel very refreshed and other times wake up and feel more groggy? It’s speculated that how you feel upon rising has a lot to do with where you are in that sleep cycle when you’re woken.

If you wake at the end of a cycle, then you get that feeling of “complete” sleep as opposed to the mid cycle grogginess.

So, when someone asks, “what’s the most appropriate amount of sleep each and every night?”
I’m hesitant to give a number of hours, but rather a more applicable/experimental answer to help you determine what works for you!

Here’s what I do. I start with the average 90 minute cycle and multiply that out by how long I want to sleep, always planning to wake at the end of that cycle. This means that my options for sleep are 4 1/2 hours, 6 hours, 7 1/2 hours or 9 hours (multiples of 90 minute cycles).

I personally go with the 6 or 7 1/2 hour options, and then set an alarm to wake up and see if I feel like I hit the end of a cycle or mid cycle (based on my scientifically valid grogginess scale…).

If using 90 minute cycles doesn’t seem to work for you, try 75 minute cycles and multiply it out leaving you with choices for 5 hours, 6:15, 7:30, 8:45 of actual sleep time. Again, see how you feel in the morning upon waking and make a judgement call based on how you feel.

In the end, you may come to the conclusion that you do your best with 7:20 minutes of sleep, which is fantastic!

There are some apps out there, and the Fitbit can help with measuring different cycles at night based on movement.

Does anyone already know the answer to how many hours a night they need to feel their best?

Thanks for reading,

Dr. Matty