Like most animals, humans need their sleep. Chronic sleep deprivation, when your body consistently doesn’t get enough rest, can lead to many health problems or even death. So each day we sleep away some 8 of out of the available 24 hours, which is a third of our lives.
Sleep recharges us, even resets us. It keeps our minds sharp, fends off physical and psychological diseases, it’s good for us. But sometimes that’s not how it feels. So what’s going on, could we sleep better? Well, increasing historic and scientific evidence suggests that we forgot the correct way to sleep…
Sleeping in modern times
After a full night’s sleep, of let’s say 8 hours, we sometimes (not always, but more often than we like) wake up feeling far from recharged. Our back may hurt, our legs feel stiff, neck and shoulders seem locked up… And it’s not something that you can solve with a bit of stretching. So why is that? If sleeping is so good for you, why can it sometimes feel so wrong?
Well, besides the fact that your body needs to start up again, lying in a virtually unchanged position for hours is often too long. Our bodies weren’t really designed to sleep for 8 hours straight. You can compare it to sitting. Modern life may require us to spend many working hours seated, but our bodies weren’t designed for that either. The fact that back pain is one of the most common health complaints in the world has a lot to with our sitting and sleeping habits.
In 2005, after 19 years of research, A. Roger Ekirch, professor of History at Virginia Tech, published the book At Day’s Close: Night in Times Past. It presents a compelling amount of evidence that humans used to divide their sleep into two separate chunks. The book includes 500+ historical references to a segmented sleeping pattern. Other historians, such as Craig Koslofsky, have endorsed these findings. According to Ekirch, most people used to sleep at night, but in two phases, separated by a period of wakefulness. People would stay awake for an hour, sometimes even a few hours.
Segmented sleep is actually still fairly common in modern society. The siesta is a popular way to recharge at midday, when our bodies often need it most. Many cultures (like Spain and many of its former colonies) have the siesta. Mostly it’s a way of escaping the sun when it’s at its highest, but the after-lunch nap serves more purposes than mere protection against overheating and sunburn. The reason that people and animals can become sleepy after lunch is driven by glucose, the sugar in food. Glucose can stop brain cells from producing the signals that keep us awake.
A siesta is a nap in the early afternoon, usually after lunch. Mostly it’s either a power nap, which like the name suggests, is short but effective, or a longer nap of up to 2 hours. NASA actually studied the power nap, and concluded that up to 26 minutes is the perfect length. When their pilots were allowed a 26-minute nap during working hours, their efficiency increased by 34%. As for longer naps, depending on the individual, they should be 90-110 minutes long. If the longer nap is interrupted earlier, the napper won’t be very refreshed.
We humans sleep in cycles of 90-110 minutes. During this cycle we go from light sleep, to gradually deeper sleep and gradually back to light sleep again, after which a new cycle starts. The last phase of the gradually lighter sleep is the Rapid Eye Movement (REM) phase, when dreaming occurs, and when breathing, heart rate and brain activity increase. This phase needs to pass uninterrupted, or we will wake up groggy and poorly rested. So in order to recharge, we should either nap up to 26 minutes (before we enter deep sleep) or nap for a full 90-110 minutes, until we have re-entered light sleep.
21st century solutions to help you sleep better
I mentioned above that sleep cycles vary per person, and that it’s important to wake up at the end of the cycle. So let’s assume that you want to try the benefits of a siesta too. It may be impossible to fit a full 90-110 minute nap into your half- or one-hour lunch, but there’s always the weekend. So let’s also assume that you have a big party-night ahead of you, then that would be the perfect time for a disco-nap. Those 90-110 minutes of sleep before the shortened night, can really help you feel better the next day.
So how do you determine your personal sleep cycle? Most of us carry these clever little computers around with us all day. And these smartphones can help us sleep better. There are apps available that can track your sleep cycle and give you personalized advice. The arguably best app is Sleep as Android, it has several features, including finding the optimal moment to wake up. Now, as the name suggests, it’s an Android app only, but there are a number of good iPhone sleep Apps too.
I’ve just started using the app, and it’s fascinating to see how much info the dashboards give you. 20th century sleep doctors often had less data to work with…