How Much Sleep Do You REALLY Need?
Consistently getting a good night's sleep is critical for ongoing health.
But what exactly is a “good night’s sleep”? And are you getting it?
Everywhere you read the same mantra, “8 hours sleep”, “8 hours sleep”, “8 hours sleep”.
If you are not getting 8 hours of sleep every night, you might feel concerned.
But is that true that you need 8 hours of sleep?
Does everyone really need the same amount of sleep?
Does the amount of sleep required vary among people?
Where does that number “8 hours sleep” come from?
How much sleep we really need
In 2015 the National Sleep Foundation updated the recommendations for sleep duration. The recommendation for adults is between 7 and 9 hours of sleep; no less than 6 and no more than 10 hours.
For adults 65 years and older, the recommendation is for 7 to 8 hours of sleep; no more than 9 and no less than 5 hours of sleep
This means, for example, that if you typically get 7 hours of sleep, you are within the recommendations for sleep duration.
The number 8 is just a number between 7 and 9, the range recommended by the National Sleep Foundation.
Where does this number come from?
Every night we cycle through phases of sleep, from light sleep to deep sleep. Each cycle lasts roughly 90 minutes. An ideal sleep is 5 cycles over the course of the night. that comes to 7.5 hours. (To read more about sleep cycles, click here).
The number 8 is not a prescription.
In fact, other sources recommend less than 8 hours of sleep.
Another study, released in 2018, claiming to be the world’s largest sleep study, with a sample size of 40,000, found that people who sleep on average between 7 and 8 hours per night performed better cognitively than people who slept more than 8 or less than 7 hours.
Other studies indicate that 7 hours is optimum and that more or less than that amount is associated with an increased risk of earlier mortality.
Reports indicating that people are not getting enough sleep use 7 hours as a benchmark.
For example, a Gallop poll in 2013 revealed that 40% of Americans get less than “the recommended amount”, less than 7 hours.
An article published in 2019 by Harvard Health said that 50% of people are getting less than the recommended amount of 7 hours of sleep.
The necessary amount of sleep varies among people
Each person has an optimum amount of sleep they require for their own body and circumstances. There is variability in the population as to what that optimum is.
Some people claim to need very little sleep. Margaret Thatcher famously declared that she needed only 4 hours of sleep (However, she succumbed to Alzheimer’s Disease, associated with sleep deprivation).
Although rare, some people do require a lot less sleep than the normal population.
These people manage with less than 6 hours of sleep and remain healthy. This is because their metabolism and circadian rhythms function differently - in a sense, all the functions of normal sleep get compressed in time, for this rare extreme in the population.
This is not the same as “getting by” on less than 6 hours night after night - and feeling tired all the time, requiring caffeine to keep you awake, and generally feeling stretched. That is an indication of sleep deprivation.
By contrast, true short-sleepers actually feel alert, refreshed, and productive on the amount of sleep they get.
There are also naturally long sleepers - healthy adults who sleep more than 9 hours each night. These are also rare in the population, as sleeping too much is normally associated with poor health.
It is thought that healthy people who sleep more than 9 hours each night may have a circadian clock that is set differently than the normal population, and so these people require more sleep.
Also read: The Secret Life of Sleep and Immunity
The amount of sleep you need changes with age
As you age, your need for sleep diminishes.
Babies and young children need up to 14 or 17 hours, older children need up to 11 or 13 hours and teenagers need up to 10 hours of sleep.
In adulthood, the need for sleep stabilizes to, on average 7 to 9 hours. This declines a bit as people age, to 7 to 8 hours of sleep, over age 65.
These numbers are averages, so of course do not apply to every individual.
This graph from The Sleep Foundation shows more specifically how much sleep is needed according to age.
Do we need a different amount of sleep according to the seasons?
There is evidence that sleep needs do change with the seasons. Certainly, we tend to feel sleepier in the winter and that is linked to lack of light.
It also makes sense that before the era of modern lighting we humans might have had no choice but to sleep longer during the winter, in higher latitudes.
If you think of your own life comparing summer and winter, you probably notice more energy in the summer and the desire for more sleep in the winter.
However, any strong seasonal variations we may have experienced in earlier times have been mitigated by our access to artificial light, effectively maintaining an artificial constant “daytime” throughout the year.