Busting the 8-Hour Sleep Myth
Updated: Nov 1, 2021
You’ve heard it before – you need a MINIMUM of 8 hours of sleep per day, but not only that, if you don’t get 8 hours, then that lost sleep accumulates through the week causing a sleep debt.
I read a blog the other day that said if you are only sleeping 6 hours per night, you would accumulate a sleep debt of 14 hours in a week and to make it up, you would have to add more sleep to your weekend and increase your sleep time during the following week.
First of all, sleeping in is bad for you. I talked about that in my previous post – Stop Sleeping In. Secondly, there’s a significant amount of research that refutes both of these ideas.
How Sleep Affects Your Health
This graph shows the relative effect of sleep on your risk of mortality. This is based on a meta-analysis of millions of people in 35 different scientific studies. What this shows is that 7 hours of sleep is associated with the least risk of mortality and getting 8 hours of sleep is associated with the same risk as getting 4 to 5 hours of sleep. This suggests that your health is not negatively impacted by getting too little sleep but by getting too much sleep.
Further, a recent major study found that cognitive performance during the day peaked for all ages at 7 hours of sleep with progressively decreasing cognitive performance occurring with sleep durations longer and shorter than 7 hours.
These studies are an indication that the human brain and body may be designed for 7 hours of sleep, not 8.
You Need a Core Amount of Sleep
Studies involving physicians in residency training, transatlantic solo yacht racers, college students, and people with chronic insomnia show that for many people a core amount of sleep of 5.5 hours is enough to perform and function, even in life and death situations.
As you can imagine, residency students are working extremely long hours, they get very little sleep, and they are put in some pretty intense situations, but they still manage to perform at extremely high levels.
This is possible because your sleep is divided into 5 stages. Stages 3 and 4 combined make up your deep sleep which is the most important sleep stage and stage 5 makes up your dream sleep, or REM sleep, the second most important stage. The research shows that your core sleep contains 100% of your deep sleep and 50% of your dream sleep, ensuring that your body and your brain have gotten the necessary rest it requires.
I know you’re thinking, “I could never do that!” But just like we have different weights and heights, our sleep needs vary as well.
But what this research really says is that as long as you have this core amount of sleep, you are still able to function and be productive. Mostly what you feel from a poor night of sleep is a bad mood about it.
The Brain Makes Up Any Missing Sleep It Needs
Lastly, the brain makes up for any missing core sleep. If you have a night where you only sleep 4 hours, in the following nights, the brain will increase deep sleep and dream sleep to make sure it makes up the lost time. What does this tell us?
Well, that you really don’t need any of that extra sleep. Core sleep studies show that the brain doesn’t even try to make up light sleep on subsequent nights and only attempts to increase the amount of deep sleep and dream sleep. This is a strong indicator that there is no such thing as an accumulated sleep debt. Your brain does not require light sleep to function, it’s just an "optional" part of your sleep pattern.
The easiest way to understand this is to compare it to food. You know you need a minimum number of calories per day for your body to function at its best. However, you often eat more due to behavioural or emotional reasons.
And just like food, where you can fast for one meal or an entire day without significant consequences, you can survive on less sleep or even no sleep for short periods without it affecting your performance.
The difference is, you tend to be a lot more anxious about missing out on your sleep.
Your True Sleep Goal
The minimum 8-hour sleep requirement and accumulated sleep debt is a myth. The research strongly suggests that as long as you have a core amount of sleep, 5.5 hours, you are able to be functional and productive, and your real sleep goal should be 6 – 8 hours per night.
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