Science Proves That Sleep is the Best Medicine

We grew up hearing the saying, "You must go to bed early and wake up early." However, once we actually become adults, we work late, cling to our smartphones, toss and turn with too many thoughts, and eventually force ourselves to open our eyes to the sound of an alarm. If mornings like this continue for several days, it feels as though something is amiss in both body and mind.

That feeling is not just a figment of your imagination. Sleep deprivation actually affects the entire body. Immunity, memory, emotional regulation, weight, and even skin. Sleep is not merely a time for rest; it is the most important time for the body to repair and reorganize itself. So why, then, are we so unable to sleep? In this article, we examine the causes that disrupt sleep and solutions you can implement starting tonight.

There are four main causes that disrupt sleep.

If you lie down to sleep but cannot fall asleep, or if you feel tired no matter how much you sleep, it is highly likely that one or more of the following four causes apply. Accurately identifying the cause is the first step toward a solution.

The First Cause — Melatonin Suppression by Blue Light

Blue light emitted from smartphone, tablet, and TV screens interferes with the brain's reception of the signal that it is night. Just looking at a smartphone for 30 minutes right before bed can suppress the secretion of melatonin, the sleep hormone, for up to three hours. This creates a situation where the body tells it needs to sleep, but the brain mistakenly believes it is still daytime. If you are curious about the impact of smartphone use on brain fatigue in addition to sleep, I recommend reading 4 Hours Without a Smartphone, My Brain Started Resting together.

Second Cause — The Residual Effects of Caffeine

The half-life of caffeine is 5 to 7 hours. This means it takes that much time for the caffeine in a cup of Americano drunk at 2 PM to be reduced by half. When you try to fall asleep at 11 PM, caffeine still remains in your body. A cup of coffee consumed late in the afternoon becomes a direct cause of poor sleep quality that night.

Third Cause — Endless Thoughts and Psychological Arousal

If you lie down and thoughts of tomorrow's tasks, unresolved problems, and worries pop into your head, your sympathetic nervous system is activated. In this state, the body cannot relax, making it difficult to fall asleep. This pattern repeats if chronic stress or an overload persists. The reason it is particularly difficult to fall asleep the night before Monday is also closely related to this psychological arousal.

Fourth Cause — Irregular Sleep Schedule

If a pattern of going to bed later and waking up later than usual repeats over the weekend, your body's circadian rhythm becomes disrupted. This is called Social Jetlag, and it is one of the main reasons why Monday mornings feel particularly difficult. If your circadian rhythm is unstable, your time to fall asleep and wake up will vary every day, and the quality of sleep will also decline.

The Effects of Sleep Deprivation on the Body

There is a reason why even a single night of poor sleep can make you irritable, unable to concentrate, and crave sweets the next day. Sleep deprivation has a tangible impact on the entire body, from the brain to the skin.

Decreased Immunity

According to research, people who sleep six hours or less a day are three times more likely to catch a cold than those who sleep seven hours or more. During sleep, immune cells are active and regulate inflammatory responses. Here is why sleep is synonymous with immunity.

Failure to control appetite

When sleep is insufficient, the hormone ghrelin, which stimulates appetite, increases, while the hormone leptin, which conveys a sense of satiety, decreases. This hormonal imbalance is the very reason why you feel particularly hungry and overeat the day after a sleepless night.

Decreased concentration and emotional regulation

Sleep deprivation impairs frontal lobe function. Judgment, concentration, and emotional regulation are all areas controlled by the frontal lobe. Reacting sensitively to minor matters or making more mistakes on sleep-deprived days is not a matter of willpower, but the result of insufficient brain recovery.

How many hours is enough — Sleep duration and sleep structure

Many people say, "I'm fine even if I only sleep 5 hours." However, sleep researchers explain this as a state of adaptation to sleep debt. They suggest that while you may not actually feel the lack, your body is already paying the price.

According to general expert recommendations, adults need 7 to 9 hours of sleep per day. Sleep repeats in 90-minute cycles 4 to 5 times, and the proportion of REM sleep increases as dawn approaches. Even if you sleep for the same 7 hours, falling asleep at 2 AM reduces the proportion of REM sleep, resulting in a different quality of sleep. Here is why going to bed early is important.

Even if you lie down for 8 hours, your body will not fully recover if you wake up frequently or lack deep sleep. The structure and quality of sleep are just as important as the duration.

5 Sleep Improvement Tips You Can Start Tonight

You don't need grand changes. A single small habit changes your sleep, and sleep changes your entire day. The following five are methods you can apply starting tonight.

Tip 1. Put down your smartphone 1 hour before bedtime.

This is the most effective tip, yet also the most difficult to practice. Try replacing your smartphone with a paper book or some light stretching. Blocking blue light alone can noticeably advance your sleep start time.

Tip 2. Fix your wake-up time first

Fixing your wake-up time before going to sleep is the key to restoring your circadian rhythm. If you keep your weekend schedule no more than an hour different from your weekdays, fatigue on Monday mornings will be significantly reduced. If you are curious about the causes and solutions for Monday morning fatigue, I recommend reading Monday Morning, Your Body Knows First as well.

Tip 3. Cut out caffeine after 2 PM

Replace coffee with decaffeinated coffee or herbal tea. You may feel sleepy in the afternoon at first, but after 2 to 3 weeks, your evenings will feel much more comfortable. Considering the half-life of caffeine, 2 PM is the cutoff point.

Tip 4. Make the bedroom a dedicated sleep space

Move TVs, smartphones, and work-related items out of the bedroom. It is important to train the brain to use the bed as a place for sleeping. The more you repeat other activities in the bedroom, the more the brain tries to maintain a state of alertness even in bed.

Tip 5. Take naps before 3 PM and within 20 minutes

If you need a nap, it is important to set a time limit. Naps after 3 PM or those exceeding 20 minutes interfere with nighttime sleep. Short naps are effective for restoring concentration in the afternoon, but if they get too long, they have the opposite effect.

Conclusion — Sleep is an investment, not a waste of time

There are four main causes that disrupt sleep: blue light, caffeine, psychological arousal, and irregular sleep schedules. If any of these apply to you, starting tonight, changing them one by one is a realistic starting point.

For too long, we have equated sleeping less with diligence. However, the concentration, stamina, and mood the day after a good night's sleep are often far better than the results of working all night. Not taking away the time your body needs to repair itself is the most productive choice in the long run.

Tonight, let's try going to bed just 30 minutes earlier than usual. Leave your smartphone out of bed, turn off the lights, and close your eyes. That time when you don't have to do anything is actually the time when your body does its most important work.

※ The sleep-related figures in this article are for general reference only. If you suspect a sleep disorder, please consult a specialist.