As so many other viral trends In social networks, in recent years a seemingly simple formula has run like gunpowder for improve nighttime rest and wake up fresh like a lettuce: Calculate the dream in 90 -minute blocks To wake up just when one ends those blocks.
This technique ensures that, when you wake up just when a complete sleep cycle ends, people They will feel more rested and with greater energy to face the day. However, scientific evidence questions the reliability of this method.
The myth of exact 90 minutes cycles
A survey of 2024 made by the American Academy of Sleep Medicine He revealed that almost one in ten American adults (9%) had tried this technique to determine what time they had to go to bed and wake up and have even been created Online calculators To make this calculation easier.
The basis of this technique is based on Natural sleep cycles that are part of the set of cycles that regulate our body known as Circadian cycles. These cycles are the ones that determine the time of sleeping, of waking up, of eating, etc.
According to this technique, a person who wants to wake up at 7:00 in the morning should go to sleep at 22:00 to complete six full -minute sleep cycles, or 23:30 to complete five sleep cycles. The concept is based on the idea that awakening at the end of a complete cycle, in phase V or REM, When the dream is lighterwould avoid the feeling of morning stun that occurs when we wake up in the middle of one of these cycles.
Sleep cycles were first identified in the 1950s, when researchers They discovered These patterns called Ultradian cycles. During the night, the alternate brain between different phases: light sleep, deep sleep and REM sleep (characterized by the most intense dreams).
Dr. Fouzia Siddiqui, Medical Director of Sentara Rockingham Memorial Sleep Center, explained in Popular Science that each of these phases fulfills specific functions for physical and mental recovery. However, the popularization of this scientific knowledge has led to excessive simplifications that They do not reflect the real complexity of human sleep. The most important of them: that the sleep cycles last exactly 90 minutes. That is the biggest problem of this theory.
Scientific reality dismantles promises
Recent studies They have shown that the duration of sleep cycles is not a constant but a variable. That is, its duration varies depending on each personand even the same person You can record more or less long cycless during the same night or vary according to the day.
An investigation He analyzed more than 16,000 nights of sleep in 573 different people found that the median duration of sleep cycles was not 90 minutes but 110 minutes, with 75% of the cycles ranging between 95 and 130 minutes. Another study based on 2,312 nights of polysomnography data determined that the average duration of the cycles was 116.9 minuteswith a standard deviation of 39.7 minutes.
In other words, establishing the 90 minutes as a basis for calculating sleep cycles not only is not an inaccuracy, but in practice it can be counterproductive since there is also the risk of interrupting the sleep cycle before it ends.
Dr. Andrea Matsumura, specialist in Sleep Medicine and founder of Sleep Goddesss Method, said In the article of Popular Science that “factors such as stress, Alcoholdiseases or even bedtime, impact on the sleep cycle, so this method does not really guarantee that you wake up less stunned. “
In addition, the studies identified that as night progresses, sleep cycles They tend to elong in a natural wayso that the former can last between 70 and 100 minutes, while the later range between 90 and 120 minutes. Making it impossible to predict at what point in the cycle You will find yourself when it is time to wake up.
On the other hand, in a standard sleep session of a healthy person, it is very unlikely be ahead of a deep phase of sleep since phase 3 of sleep, the deepest and repairinglasts between 20 and 40 minutes and usually occurs in the middle of the sleep session, and then move back to phase 2 which is a relaxing but lighter dream.
Therefore, unless you are sleeping very few hoursthe awakening occurs from that lighter phase, and not from a deep phase as the 90 -minute block theory supports, which would leave a greater feeling of stunning.
That is, this theory is based on two real facts: that awakening from phase 3 leaves you more stunned and that sleep cycles last around 90 minutes, to set up an alleged infallible technique to wake up as a rosto. The problem is that sleep It is not an exact science And the only thing that really works is Ensure the Descaso Hours that the body needs … and there are not even certainties about How long is needed.
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