⚠️ Warning ⚠️: This article will be controversial and may contain information biased towards my point-of-view.

Now that we got that out of the way I would like to talk about sleep. Not just sleep, but about the way people talk about it and about the studies that come up with magic numbers based on massive amounts of people with entirely different backgrounds (physically, mentally, daily routine-wise).

Recently I've seen many articles popping up about sleeping habits, the way humans should sleep, the magic number of how many hours you need and the way you should rest together with hundreds of gadgets or apps that will help you fall asleep and wake up refreshed.

How do you know how much sleep you need?

Well, not from studies focusing on other people. Sleep is one of the most mysterious things we do, and some people spend half of their precious 24 hours on it because they don't understand how it works.

Almost all studies take subjects from various backgrounds and compose an average, but when publishing results, most people skip over these details. A scientist can make an experiment turn in their favor in countless ways. Look at this, this or this to only mention a few. What's even worse is that most people (I would say 80%, but this is a vague estimate) only read news articles about the studies, that are further biased, sponsored, the author might not understand what they talk about, or it's generally not precise enough to draw any logical conclusion.

So now we have a fantastic and extremely abstract topic called sleep. News sites connected sleeping less than 7.5 hours with Alzheimers, cancer and so many different things. The problem is that the patients might have had various factors in their life influencing the development of such disease. For example a recent study found that the environment you grow up in contributes to later developing Alzheimer's. Since the closest you can get to isolated subjects are rats and the brain of rats is still a lot different from humans we can't tell if sleep causes these issues or something else.

Yes, some facts are tough to argue with. The REM and deep sleep states for memory and regeneration have been monitored with MRIs and a bunch of other experiments/machines many times. On the other hand, you can't track how much sleep someone needs generally. The best effort scientists made was measuring brain output (completing creative or difficult tasks) when subjects slept well and when they slept in wrong ways, but this is an extremely short-term conclusion (usually subjects have been called in for only 2 days), and scientists didn't measure what they ate, worked out and so on for weeks before. Even the period between experiments might change results or just that the subject is not in their home, but in a hospital or an unfriendly environment. I am sure I would need a bit more time to fall asleep if I was in an uncomfortable hospital bed.

7.5 hours

This is the magic number. If people sleep above this, they will be healthy and will live a full life, if you sleep under you die of cancer, right?

I don't believe in magic numbers drawn from vague long-term conclusions. For example, I usually wake up after 4 hours of sleep and feel more refreshed, than when my alarm wakes me up after 9. (This is almost every day, by the way, my body kicks me out of bed, and except taking a nap midday I can't really do anything about it).

The way I tested how much sleep I need was by A/B testing the hell out of it for years. It's not a short journey.
Successful businesses A/B test lots of things. Your body unconsciously A/B tests food by creating cravings, you A/B test products or tools when switching between them back and forth for specific tasks, but only very few people A/B test sleep. Instead, they set the alarm for 7.5 hours from now and wake up hoping they will be happy and healthy afterward.

I am not saying you should sleep for 4 hours. I have seen people feeling the worst all day because they tried my methods. In fact, I'm the only one I know who can sustain 2-4 hours of sleep without almost any caffeine intake combined with an "unhealthy" diet (I eat lots of meat, barely any vegetables and some sides. Minimal sugar and close to no caffeine). It works for me, but it likely won't for you.

If you need to rely on caffeine in the morning your body is trying to tell you it's exhausted or that you've built an addiction. If you are yawning your body is saying it's tired and you should go to sleep. There is no shame in napping midday. I often get myself up to speed with a 30-minute quick nap, even if my day is packed with things to do.

What's the point of this article?

People, don't rely on vague scientific facts. Experiment with your own body. If you know your body and mind, you will be able to control your life more than anyone else around you and don't try to fit other people's routines on yours.
A/B test routines as aggressively as you would test your product's features.

Make sure you minimize the external differences between the preparation for tests. This can mean eating the same meal, exercising the same amount, working the same hours and countless other factors depending on your life.

This piece of article is my opinion, and I hope you will take it with a grain of salt. Please validate any point I made and don't fall into the trap of believing another stranger telling you what to do.
One of the main reasons I wrote this article is to send it to people telling me how I should sleep or not sleep and to help people who follow the latest trends of minimal sleep (Silicon Valley, I'm looking at you) rethink their choices. No one knows what effect throwing your body out of balance might have on you. No one, but you in 20 years and until time travel is discovered you might be doing permanent damage to your body by sleeping too much or too little compared to what's natural. If you move to another city or another place you need to redo all of your tests and maybe you should record data points densely to see what fits you best.

Take care of your body, your mind and remember that your body knows itself best, not someone on another continent.