Only young parents can maintain such sleep pattern in a long run. For the rest of us it’s dangerous

Every now and then, a story pops up about someone who “saves a lot of time” by sleeping just a few hours a day. If that sounds too good to be true, that’s because it is.

Let’s start with stating the obvious – the required amount of sleep is a highly individual thing. But only very few of us are able to regularly go on 2-4 hours of sleep a day. That’s due to a rare genetic condition – the DEC2 mutation. Only estimated 1% of people have this “ability.” The rest of us have to sleep at least 6-7 hours to function properly. What you might have heard of is polyphasic sleep – the kind of sleep where you fall asleep just for a few hours, but repeat the process a couple of times during the day/night.

One particular type of polyphasic sleep is biphasic and in fact, that’s the sleep pattern we all followed until relatively recently. Until the 19th century, we slept biphasically. What does that mean?

We slept in two parts. We went to bed after dusk and slept for a couple of hours, until around midnight. Then, we’d wake up, add wood to the fireplace, attend to children, check if all is safe, have sex and after a few hours, we’d go back to sleep. We slept biphasically for tens of thousands of years – with our sleep divided into parts lasting just a few hours each. That changed in the 19th century.


We have our cities and the Industrial Revolution to thank for that.

The first modern central heating system was developed in the late 18th century. That freed us from freezing at night and getting up to add wood to the fire. Additionally, gas lamps and, later on, electricity saved us from having to go to sleep just after sunset.

Now, the predominant sleep pattern is monophasic – we go to bed, hopefully get some sleep and get up after however many hours it is we get. Even if we experience some nighttime awakenings, they typically last minutes, not hours.

As you can see, over time, some of our sleep patterns have drastically changed. But you know what hasn’t changed? The amount of sleep we need to function properly. No matter which way you cut it, it still has to be at least 6 hours and preferably 7-9 hours a day. And keep in mind, when we slept biphasically, at the end of the day, the amount of sleep we got was in general greater than today.

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The same city lights we enjoy so much today cause one of the most widespread and dangerous epidemics in our history – insomnia. Truly dark nights devoid of man-made lights are virtually unattainable anymore. We are continuously surrounded by light in every form – from street lights to the blue light of our smartphones – and that’s one of the main culprits responsible for the insomnia epidemic.

There are instances where it is possible to sleep just a couple of hours a night, but these are an exception rather than the rule. For example, young parents, taking care of their baby. Such sleep patterns, however, can only be sustained for up to three months – otherwise, they cause potentially serious health problems. So, to answer our original question – no. We already sleep less than our ancestors did and have to put up with every possible sleep-disrupting invention you can think of. Cutting into it even more, won’t do you any favors.