Sleep Education Day (Min'iku no Hi) — 3/19, from "mi (3) - i (1) - ku (9)"

What Is Sleep Education Day?

March 19th is celebrated every year as "Sleep Education Day" (Min'iku no Hi). It was established by Nishikawa Living Inc., an Osaka-based maker of bedding (now part of Nishikawa Co., Ltd.), and registered with the Japan Anniversary Association in 2018. The date comes from a wordplay on the numbers: "mi (3) - i (1) - ku (9)" reads like "min'iku" (sleep education). "Min'iku" means activities that build healthy sleep habits and support children's growth. The day aims to help people understand how important sleep is for children's development and to spread sleep education across all generations.

Sleep and Development

Important processes that maintain the brain and body take place during sleep.

• Growth hormone release: Growth hormone is said to be released mostly during the first deep (non-REM) sleep after falling asleep. It is involved not only in children's growth but also in repair and metabolism in adults.
• Memory organization and consolidation: During sleep, the brain is thought to sort information learned during the day and consolidate it into memory. Cutting sleep to study can actually make learning less efficient.

The Body Clock and Melatonin

The human body has an internal clock — the circadian rhythm — that runs on roughly a 24-hour cycle.

• Morning light and nighttime sleep: Exposure to sunlight in the morning resets the body clock, and roughly 14 to 16 hours later, the "sleep hormone" melatonin is said to be released.
• Watch the light before bed: Bright light from smartphones and similar devices before bed is said to suppress melatonin and make it harder to fall asleep.

Interesting Facts About Sleep

• Individual differences in the "90-minute cycle": REM and non-REM sleep are said to alternate in roughly 90-minute cycles, but this varies from person to person and doesn't apply uniformly to everyone.
• The role of dreams: Dreams during REM sleep are thought to help process emotions and relieve stress.
• REM sleep behavior disorder: Normally, muscles are kept still during sleep, but there's a condition where this control fails and the body moves in response to dream content.
• Short sleepers: In OECD surveys, Japan's average sleep time is among the shortest of member countries.
• Short naps: Japan's Ministry of Health, Labour and Welfare sleep guidelines have recommended a nap of 30 minutes or less in the early afternoon when you feel very sleepy, and some companies encourage napping.

Tips for Enjoying Sleep Education Day

• Open your curtains right after waking up and soak in plenty of sunlight to properly reset your body clock with a "morning light routine"
• In honor of March 19th, reassess whether your pillow height and mattress firmness suit you, and create the ideal "bedroom environment" for great sleep
• Put away digital devices an hour before bed and wind down with reading or light stretching
• In families with children, set regular bedtimes and wake-up times for everyone to keep a steady daily rhythm

Deep, Restful Sleep Fuels Your Best Performance Tomorrow

March 19th is a day to allow yourself the "best rest" possible, resetting your mind and body and recharging your energy for tomorrow. Quality sleep is the foundation of healthy days. Valuing sleep is the same as treating yourself with care. When you wake up with a brain and body that are fully recharged, the world looks brighter and full of possibilities. May today lead to peaceful sleep and a refreshing wake-up tomorrow!