“Sleep Well, Live Better.” This is the official slogan for World Sleep Day 2026, observed this year on March 13th. Established to raise awareness of sleep’s vital role in global health, the day serves as a reminder that sleep is not merely downtime, but a sophisticated biological process essential for recovery.
Despite its importance, modern society faces a sleep crisis. According to a January survey of 1,000 adults by the Korean Sleep Society and Simmons, 69.2% of respondents failed to meet the minimum recommended seven hours of rest. To help bridge the gap between sleep science and daily habits, we explore the most common questions regarding nocturnal health.
Q1. Why is sleep considered a period of "recovery"?
While we rest, the brain and body perform essential maintenance that is impossible during waking hours. This includes consolidating short-term information into long-term memory and flushing metabolic waste from the brain.
Professor Shin Jeong-won, a neurologist at Bundang CHA Hospital and director of the Korean Sleep Research Society, notes that hormones such as leptin, ghrelin, cortisol, growth hormone, and insulin are all governed by sleep. For example, leptin signals satiety; when you sleep well, your brain effectively suppresses appetite. Conversely, a lack of sleep spikes ghrelin, the hunger hormone, which explains the common impulse to reach for late-night snacks when tired.
Additionally, sleep regulates cortisol, the stress hormone. Chronic insomnia keeps cortisol levels elevated, which can trigger systemic inflammation and hinder blood sugar control—making adequate sleep a critical priority for patients with diabetes and high insulin resistance.
Q2. Is it true that children must sleep before midnight to grow taller?
Contrary to popular belief, there is no "magic window" between 10 PM and midnight for growth. Growth hormone is not strictly tied to the clock, but rather to the quality of the sleep cycle.
"While small amounts of growth hormone are secreted during the day, 70–80% is released during sleep," Professor Shin explains. "This occurs specifically during deep sleep, also known as slow-wave sleep." As the body cycles through light, deep, and REM sleep approximately four to five times a night, the priority is reaching those deep-sleep stages consistently, regardless of the exact hour the head hits the pillow.
Q3. Does growth hormone matter for adults and the elderly?
Yes. While the name suggests it is only for children, growth hormone remains essential throughout adulthood. It regulates bone density, maintains muscle mass, assists in fat metabolism, and is fundamental for cell repair and tissue regeneration. Although its secretion naturally tapers off with age, maintaining high-quality sleep ensures that the body can continue to repair itself effectively throughout the later stages of life.
Q4. What habits can improve sleep quality tonight?
To combat insomnia, one must lower the body’s "arousal level" before bed. The most significant modern disruptor is the smartphone. Using a device in the dark tricks the brain into perceiving daylight, which suppresses the secretion of melatonin, the hormone that signals sleep.
At a World Sleep Day 2026 symposium held at Seoul St. Mary’s Hospital, Associate Professor Um Yoo-hyun of Catholic University emphasized the importance of "stimulus control." Her advice includes:
The Bed is for Sleep Only: Avoid working, eating, or browsing on your phone in bed so your brain doesn't associate the space with alertness.
The 20-Minute Rule: If you are tossing and turning for more than 15–20 minutes, get out of bed. Only return when you feel physically sleepy.
Temperature Control: As we fall asleep, our core body temperature naturally drops. Keeping the bedroom slightly cool and taking a warm shower 1–2 hours before bed can facilitate this thermal shift, making it easier to drift off.
