How Little Can You Sleep?
We’ve discussed how much sleep you need (at least seven hours, for most people), but often our real question is the downside: can you get away with less than the optimal amount, or even replace your night’s sleep with a series of round-the-clock sleep ?
Everyone has different needs, but six hours is probably the minimum.
“We don’t have to talk about how much sleep people need, other than how many calories we need,” says sleep specialist Dr. W. Christopher Winter . Just like 2000 calories is not the right amount for everyone, nor is it a universal number like eight hours of sleep. If you are sick or exercise a lot, you may need more sleep. And as you get older, you probably need less.
According to the National Sleep Foundation , adults need to get seven to nine hours of sleep every night. The Foundation team reviewed the research and used their own clinical experience to arrive at these numbers, as it is impossible to conclusively determine how many hours a person needs. Seven-nine is in line with the available evidence.
The group noted the wider range, from six to ten hours, as “might be appropriate”. This is the range for adults between the ages of 26 and 64; eleven hours may be enough for young people, and nine hours maximum for those 65 and older. This does not mean that everyone will be all right with six hours. This means that some people who sleep six hours each may have trouble sleeping, but for others, six hours is just what their body needs.
Dr. Winter previously reminded us that people often sleep more than they think, so check with your Fitbit if those numbers don’t seem realistic.
Bad things happen when you don’t get enough sleep.
Whatever your personal minimum, you don’t want to lower it regularly. Check out what the National Sleep Foundation’s panel of experts found for young people (18-25):
The group does not recommend sacrificing sleep for school, work or social responsibilities because short sleep is associated with increased fatigue, decreased psychomotor function, accidents, poor physical and psychological health, and poor academic performance.
And similarly for adults from 26 to 64 years old:
The negative effects of sleep deprivation on multitasking, weight regulation, job safety, mental health, blood sugar regulation, blood pressure, and cardiovascular health have been reported, especially on nighttime sleep deprivation during the work week.
The consequences of sleep deprivation extend beyond mere drowsiness. In addition to the effects mentioned above, you may lack the judgment to make ethical decisions , or you may be more likely to gain weight over time. Lack of sleep can increase the likelihood of dying from a heart attack .
In the long term, work schedules that tend to disrupt employee sleep are on the IARC’s list of “probable” causes of cancer . This is the same category as red meat, hot drinks, and the pesticide glyphosate. To clarify, we don’t know for sure if shift work is a carcinogen, but there are enough links between sleep deprivation and poor health that this idea is not far-fetched .
No, sleep probably won’t replace sleep
Until now, we have assumed that you sleep all or most of your sleep in one large portion of the night. Longtime Lifehacker readers may remember that polyphasic sleep was all the rage a few years ago: just do six tiny daytime naps a day and you can give up the whole thought of getting a good night’s sleep. If it worked, it would be the most time-saver.
It is assumed that great thinkers throughout history have slept very little or worked on erratic schedules – classic examples are Leonardo da Vinci and Thomas Jefferson. But these stories don’t really stand up to scrutiny , and luckily all of these geniuses are dead and cannot be questioned.
So we asked Dr. Winter if naps could actually replace sleep. He was not impressed:
The proponents of polyphasic sleep have nothing but anecdotal experiences that are never confirmed by rigorous testing … I would say with confidence that the science of sleep will almost always fall into a corner, claiming that this life hack is a fake.
Just to be clear, comfortably long naps is still fine, and if it’s part of your daily routine, you can continue. Small children also need naps. But if you want to get some sleep to get through the day, you probably haven’t gotten enough sleep at all.
The idea of polyphasic sleep as a productivity tool was inspired by research like this one published in Work And Stress , which examines how crews in sailing races can stay vigilant around the clock. The sailors did not sleep at night, because it was then that collisions and troubles were more likely, so they had no choice but to take a nap during the day. The most productive sailors slept from 20 minutes to an hour.
Sleep can help you regain some alertness when you don’t get enough sleep, and with enough sleep, sailors could remain in working order for several days. However, the more they slept, the better they ran.
Sleep-oriented sleep patterns do not seem stable. Bloggers who popularized the idea of polyphasic sleep usually left this extreme form after a few months , returning to a regular regimen with a block of night sleep and, for some, daytime sleep. (I searched, but couldn’t find anyone who slept around the clock for many years.)
So, whether you like it or not, the sleepover isn’t going anywhere. If you don’t get enough sleep at night, sleep can help you survive, but for a healthy mind and body, you need to work at least six hours a day, and for most of us, probably seven. or more.
Illustration by Jim Cook.