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How do you wake up in the morning? Do you wake up feeling refreshed and alert at the same time every day? Many people probably feel like they haven't slept enough even after getting sufficient sleep, have trouble waking up, or feel groggy and unfocused even after they're awake. You may also have experienced oversleeping because you didn't notice your alarm.
Here, we will introduce "The 10 Best Sleep Methods" recommended by Seiji Nishino, author of the currently popular book, "The Stanford Way to the Best Sleep."
This first installment focuses on setting your alarm for waking up.
Two-stage alarm setting
How do you set your alarm?
While some people may not use an alarm clock at all, most people probably set it to ring once, or multiple times if they have trouble waking up. Many people who set it once also use the snooze function to make it ring again after a short interval.
In this article, we will introduce Professor Nishino's recommended alarm settings. By implementing them, you should find it easier to wake up in the morning than usual.
The recommended alarm setting is a "two-stage setting." "Two-stage" means setting the first and second alarms about 20 minutes apart. The first alarm should be set to a "very low volume and short duration." For example, if you want to wake up at 6:30, set alarms for 6:10 and 6:30. You should be able to wake up smoothly at one of these times.
Reasons for setting a two-stage alarm
Our bodies secrete or suppress various hormones in response to circadian rhythms and external stimuli such as light. One of these is cortisol, a hormone that regulates blood sugar levels.
This hormone is secreted at its highest level in the early morning, gradually decreases thereafter, and is hardly secreted during the first half of sleep. Its peak secretion in the early morning signifies preparation for daytime activity (wakefulness).
Furthermore, sleep consists of non-REM and REM sleep. Non-REM sleep is when the body and brain rest, whereas REM sleep is when the body rests but the brain is active. Non-REM and REM sleep alternate, and these sets typically have a cycle of about 90-120 minutes, though this varies from person to person.
Deep non-REM sleep occurs more frequently in the early stages of sleep, but as the cycles progress, shallow non-REM sleep increases towards morning. The proportion of REM sleep also increases. Therefore, the proportion of REM sleep is higher in the morning.
In other words, in healthy sleep, the body prepares to wake up from early morning. To wake up even more refreshed, it is desirable to wake up during shallow REM sleep or heightened REM sleep during the period of preparation for awakening.
Some might think that it would be effective to detect shallow non-REM sleep or REM sleep that occurs in the early morning using wearable devices. While wearable devices acquire and utilize vital data using accelerometers, gyroscopes, heart rate sensors, etc., to detect sleep (※1), they are becoming capable of detecting the depth of non-REM sleep, but currently, the detection of REM sleep is not accurate.
Recently, simple sleep tracking apps have emerged, but their accuracy in determining sleep stages is inferior to wearable devices, and they cannot correctly determine REM sleep. Furthermore, some opinions point out the disadvantages of using smartphone tracking apps, such as increasing anxiety (※2). Therefore, it is not realistic to try to accurately detect REM sleep at home on a daily basis.
Therefore, we recommend setting a two-stage alarm as a simple way to stimulate you during the preparation period for awakening, specifically when non-REM sleep has become shallow or during REM sleep.
In the early morning, non-REM sleep naturally becomes shallow and shorter, and REM sleep becomes longer, so there is a higher probability that one of the two alarms will coincide with a time when it is easier to wake up.
If you happen to be in deep non-REM sleep during the first alarm, being forcibly woken up from deep sleep by a loud alarm will result in a poor wake-up. This state of feeling groggy and unfocused even after waking up is called sleep inertia, and it occurs when you are forced to wake up from deep sleep.
To avoid waking up during deep non-REM sleep, it is important to set the alarm to a "very low volume and short duration." Since the frequency of REM sleep is probabilistically higher in the early morning, even if you don't wake up with the first alarm, you can wake up with the second alarm.
"It's the weekend, I don't need to wake up early, so I'll sleep a little longer" is not good.
On days when you don't need to wake up early at your usual time, you might extend your wake-up time, turn off your alarm, and go back to sleep for a second or third time. You might think, "It's the weekend, it's fine," but this has many disadvantages: it disrupts your sleep rhythm, leads to insufficient wakefulness, makes it harder to sleep after waking up in the middle of the night, and makes it harder to form deep non-REM sleep immediately after falling asleep.
The instinctive desire to sleep is a sign that you have accumulated sleep debt, so it is important to sleep when you feel the urge. However, sleeping in on weekends for a second or third time does not fundamentally solve sleep debt. If you tend to sleep in on weekends, try increasing your weekday sleep by just 30 minutes each day.
If you feel like "sleeping a little more" on your day off, first wake up at your usual time, get some sunlight, eat breakfast, and then take a nap of about 20 to 30 minutes when you feel drowsy in the early afternoon. A nap of this duration will have minimal impact on your nighttime sleep, making it less likely to disrupt your sleep rhythm. A consistent sleep rhythm will also make Monday mornings less dreadful.
However, this method does not fundamentally solve sleep debt. It is important to maintain a consistent sleep rhythm and ensure you get enough sleep every day.
【References】
※1:Current Status, Problems, and Future Prospects of Systems Utilizing Wearable Devices
※2: Sleep Tracking: Could It Be Making Your Sleep Worse?
