Are You Swayed by the "8 Hours of Sleep is Best" Myth?

"I slept a lot but I don't feel refreshed at all." "I only slept 6 hours but my body feels great." Everyone must have experienced this at some point. The established theory often seen in the media and books states that "8 hours is the ideal sleep duration," but in reality, this is not an absolute rule applicable to everyone.

Human sleep is heavily influenced by factors such as age, genetics, constitution, and daily activity levels. The best sleep duration for one person might be "sleep deprivation" for another, or on the contrary, "oversleeping."

The important thing is not conforming to media information or other people's standards, but rather, finding "the sleep duration that maximizes your performance (My Sleep Cycle)."

This article clearly explains the specific calculation methods to find your perfect sleep duration, from average sleep times by age to discovering your own.

Ideal Sleep Duration Changes with "Age"

As a major premise, it is scientifically proven that the required sleep duration naturally decreases as we get older. Let's look at the recommended sleep duration by age published by the National Sleep Foundation in the US.

Infants (1-2 years old): 11 to 14 hours
School children (6-13 years old): 9 to 11 hours
Late teens (14-17 years old): 8 to 10 hours
Adults (18-64 years old): 7 to 9 hours (on average, 7 to 7.5 hours)
Seniors (65+ years old): 7 to 8 hours (or less)

As this data shows, "8 hours" is merely one guideline falling within the range for teens to adults. As you age into your 40s and 50s, "not being able to sleep 8 hours" is a remarkably natural bodily change, and in most cases, it is neither a disease nor insomnia. Unreasonably forcing yourself to stay in bed for 8 hours can paradoxically lead to shallower sleep and middle-of-the-night awakenings.

How to Find "The Sleep Cycle that Suits You"

So, how do we find the sleep duration that is genuinely the best for us? The key is an experiment utilizing the "90-minute sleep cycle," where human sleep continually cycles between light and deep stages.

Step 1: Set an Initial Goal Based on a "Multiple of 1.5 Hours"

First, set a foundational goal time that aligns with the cycle of sleep.

For adults, it is realistic to choose from the following 3 patterns.

6 Hours (90 mins × 4 cycles)
7.5 Hours (90 mins × 5 cycles)
9 Hours (90 mins × 6 cycles)

It is said that when many adults set "7.5 hours" as their base, they are less likely to feel sleepy during the day and their performance rises. Let's try setting "7.5 hours" as your provisional best time for now.

Step 2: "Experiment" by Finetuning the Duration Weekly

Once you've decided on a "provisional best time," try living under the following conditions for a week.

Fix your bedtime (e.g., Going to sleep every night at 11:30 PM).
Record the time you wake up naturally without an alarm (It's best to perform this during a week with holidays or mornings with spare time).

[How to Judge the Experiment]

Woke up refreshed before the alarm! I'm not sleepy during the day! 👉 That duration is your ultimate best sleep time.
Can't wake up even when the alarm goes off. Sleepy during the day... 👉 You are not getting enough sleep. Next week, try pushing your bedtime earlier by 15 to 30 minutes (sleeping longer).
Waking up multiple times in the middle of the night. Waking up earlier than planned and can't go back to sleep. 👉 It's possible your sleep duration is too long. Next week, try pushing your bedtime later by 15 to 30 minutes (sleeping shorter).

Repeat this "15 to 30-minute" finetuning every week. The duration where "you snap awake naturally without an alarm and aren't hit with strong drowsiness until evening" is your exclusive ideal sleep duration.

A Tool to Easily Calculate and Record Daily Cycles

Once you have identified your perfect sleep duration (for example, "7 hours and 15 minutes"), it is crucial to control your daily bedtime and wake-up time according to that length.

However, calculating mentally every time, like "I have to wake up at 6:00 AM tomorrow, so working backward 7 hours and 15 minutes is..." is surprisingly tedious. In those moments, we recommend using the tool below.

Sleep CalculatorWhat time should I sleep? Calculate your 90-minute sleep cycles to wake up refreshed.

With this tool, the following calculations are completed in a flash.

Work Backward from "I want to wake up at X:XX" to "I should go to bed at X:XX" If you choose your ideal sleep duration (for example, "4-5 cycles"), it will quickly tell you exactly "What time you should get into bed."
Accurate Calculation Considering Sleep Latency (Time Until Falling Asleep) You can calculate a much more precise timing for bedtailored to your habits, such as "It takes about 15 minutes to drift off after getting under the covers."

By employing it to manage your daily sleep schedule, constantly maintain your finest cycle.

Tips for Creating "High-Quality Sleep," Which is Just as Vital as Sleep Duration

Once you've figured out a sleep duration that suits you, what becomes exceedingly more paramount is "sleep quality." No matter how much time you secure, it's meaningless without quality.

Lastly, here are "4 rules for producing high-quality sleep" that you can start practicing today.

1. Reset Your "Internal Body Clock" by Bathing in Morning Sun First thing when you wake up, pull back the curtains and bask in the sunlight. Exposure to sunlight puts a halt on sleep hormone (melatonin) secretion and sets a timer for drowsiness to arrive approximately 14 to 16 hours later.

2. Finish Bathing 90 Minutes Before Bedtime Humans feel incredibly sleepy exactly when their "core body temperature (deep body temperature)" dips. Taking a bath (in a tub) about 90 minutes prior to bedtime to raise your body temperature effectively ensures it drops just when it's time to get in bed, facilitating a smooth transition into deep sleep.

3. Strictly No Smartphones or PCs Right Before Bed The blue light emitted from screens resembles "sunlight," tricking the brain into thinking "it's still daytime" and suppressing melatonin secretion. Ideally, you should put devices down an hour before sleep and relax with reading or light stretching.

4. Do Not Shift Your "Wake-up Time" Even on Weekends Continuing a routine of "since I'm sleep-deprived on weekdays, I'll binge-sleep on the weekend" severely skews your internal clock, rendering Monday mornings phenomenally grueling. The ultimate secret to regulating a week's rhythm is to keep the deviation between weekday and weekend wake-up times to within a maximum of 2 hours, even when you sleep longer on the holidays.

FAQ

Q1: Do short sleepers and long sleepers genuinely exist? A: Yes, they do exist. "Short sleepers (healthy on less than 6 hours)" and "long sleepers (fall ill unless sleeping over 9 hours)" are largely considered to be due to genetic factors. However, they are exceedingly rare cases representing far less than 1% of the total population. For a vast majority of people, their ideal duration settles comfortably between "7 to 8 hours." Heedlessly aiming to become a short sleeper harbors the risk of deteriorating your health, so we do not advise it.

Q2: Is utilizing a sleep app for measurement effective? A: Yes, they offer immense clues to understanding your sleep cycle. Smartwatches and sleep apps visualize the waves of "REM sleep" and "non-REM sleep" based on your body movement and heart rate. That said, as they are not flawlessly accurate, make your primary criterion "how refreshed you feel during the day (subjective physical condition)."

Q3: What should I do on a day I unavoidably stray past my bedtime? A: To avoid shattering your rhythm, the ironclad rule is to "not change your wake-up time." Even if you hit the sack two hours later than normal, rouse yourself up precisely at the regular hour (it will be arduous during the day), and then make a point to sleep earlier that night to compensate. If the exhaustion is unbearable, cover it by taking a "15 to 20-minute power nap" in the afternoon.

Summary

"8 hours of sleep" is not an absolute scientific rule. What's essential is figuring out "Your Optimum Time" matching your age and constitution.

Sleep duration naturally dwindles with age.
First, use "7.5 hours (90-minute cycle × 5)" as a baseline, and explore the prime time suited for you by making 15 to 30-minute adjustments.
Being able to "wake up without an alarm and not feel sleepy in the daytime" is your 'My Sleep Cycle'.

For troublesome daily schedule calculations, automate them using the tool below. Ascertain your unique, perfect sleep duration and propel your daily performance to pinnacle levels.

Sleep CalculatorWhat time should I sleep? Calculate your 90-minute sleep cycles to wake up refreshed.