Recommending exactly eight hours of sleep to everyone is inaccurate and unspecific advice, and not valid for anyone at any age.
For decades, the phrase "sleeping eight hours is healthy" has been penetrating deep among the population. However, as with practically any general health advice, it is a statement that must be qualified. It is not true, but it is not wrong either, rather it is an inaccurate statement.
In fact, Dr. Jade Wu has recently spoken on this subject on the well-known scientific website Scientific American, once again confirming something that various groups of researchers have suggested in multiple studies for years: sleeping eight hours is a myth. Sleep is important, but not everyone requires the same number of hours.
As Wu well recalls, sleep is essential , and he emphasizes a well-known phrase from Shakespeare, where the playwright speaks of sleep as "the bath of painful childbirth, the balm of wounded minds, the second course of great nature, the main food of the feast of life". He who does not sleep dies, although not immediately, since long before a fatal outcome, various adverse effects linked to sleep restriction are known.
For example, Wu cites a meta-analysis that included data from 1,600 participants, suggesting that sleep deprivation leads to reduced attention and impaired thinking in general. Likewise, it is known that lack of sleep also causes alterations in mood, both in the short and long term. And, according to more recent studies, it can also alter the gut microbiome.
Measuring the hours of sleep and giving generalized advice to the entire population is unscientific, as Wu rightly comments, making use of a comparison with the amount of water needed daily. We now know that "drink eight glasses of water a day" or "two liters of water a day" is wrong advice, and that hydration and water needs can vary greatly between individuals, depending on diet and level of daily physical activity. So advice on sleep needs also varies individually.
According to the psychologist, the amount of sleep each person needs will depend on individual biology and bodily needs. For example, the guide published in 2015 by the National Sleep Foundation of the United States already concluded that just taking into account age, sleep needs should already be different.
According to this guide, in the adolescent age it would be advisable to sleep between 8 and 10 hours, but even a range of between 7 and 11 hours could be appropriate without problems. For its part, in the case of newborns , the range ranges between 11 and 18 hours of sleep.
On the other hand, people over 65 years of age can reduce their sleeping hours without this causing health problems, being able to sleep between 5 and 9 hours without problems according to the guide. For this reason, according to Wu, a "healthy sleep" does not imply a fixed number of hours forever, but rather that said time can vary not only between individuals, but in the same person, the sleep time will vary with age and will be something completely different.
In the case of adulthood, the typical eight hours would be only a happy medium for Wu, although he ends his article by giving three simple tips to detect what is the appropriate sleep time for each individual:
1. Being "tired but connected" indicates sleeping too much: For Wu, being "tired but connected" refers to being awake in bed, tossing and turning and trying to fall asleep too early, or trying not to wake up too early. If this situation occurs constantly, it means that you are trying to sleep more than the body needs.
2. Being sleepy during the day means not getting enough sleep at night: Although for Wu this is an obvious situation, it suggests that daytime sleepiness is often not taken seriously. Although sometimes this drowsiness has an explanation, such as having prolonged a night too long on time, on other occasions it does not. If it is something habitual, it means that you are constantly getting little sleep, and it is something that must be changed and improved.
3. Maintaining a constant sleep is essential: Maintaining sleep schedules, not only in quantity and quality, but also respecting a few hours each day, is important for a restful sleep. Going to bed and waking up at approximately the same time, and sleeping approximately the same amount of hours, is not the same as sleeping four hours one day and compensating for the next with ten hours. For Wu, the third and last point would be "maintaining a stable schedule", thus being able to generate adequate daily sleep.