World Sleep Day, a day dedicated to a fundamental aspect of our well-being

World Sleep Day (the Friday before the northern hemisphere vernal equinox) is an annual event organized by the World Sleep Day Committee of the World Association of Sleep Medicine (WASM), since 2008. The goal is to celebrate the benefits of good and healthy sleep and to draw society's attention to the burden of sleep problems and their medical, educational, and social aspects, and to promote the prevention and management of sleep disorders.

This special day aims to reduce the burden of sleep problems on society, which threaten the health or quality of life of as much as 45% of the world's population.

This year the day is today, Friday 13 March 2020. Events involving discussions, presentations of educational materials and exhibitions take place around the world and online.

The first curiosity about the World Sleep Day is that it has a new slogan every year:

• 2008 “Sleep well, live fully awake”
• 2009 “Drive alert, arrive safe”
• 2010 “Sleep well, stay healthy”
• 2011 “Sleep well, grow healthy”
• 2012 “Breathe easily, sleep well”
• 2013 “Good sleep, healthy aging”
• 2014 “Restful sleep, easy breathing, healthy body”
• 2015 “When sleep is sound, health and happiness abound”
• 2016 “Good sleep is a reachable dream”
• 2017 “Sleep soundly, nurture life”
• 2018 “Join the sleep world, preserve your rhythms to enjoy life”
• 2019 “Healthy sleep, healthy aging”

And the new one? 2020, “Better sleep, better life, better planet”

It’s clear how sleep is closely linked to the psychophysical health of the human being, in a balance of factors among which sleep remains one of the protagonists.

Circadian cycles

Introduction

The earth is a rhythmic environment. The temperature, rainfall and daylight vary with the seasons: light and dark alternate every day, tides rise and fall. In order to be truly competitive, and therefore to survive, an animal must have a behaviour capable of fluctuating with the cadences of its environment.

The brain has created a wide variety of rhythmic control systems. Sleep and wakefulness are the most obvious periodic behaviors.

Some rhythms controlled by the brain, however, have much longer periods, like the hibernation of the animals, while others have shorter periods, like the cycles of breathing, the steps of walking, the repetitive stages of a night of sleep and the electrical rhythms of the cerebral cortex. The functions of some rhythms are obvious, whilst others are still obscure, and some rhythms are indicative of pathology.

Almost all physiological functions of the body change according to daily cycles known as circadian rhythms. The clocks that govern circadian rhythms are in the brain, are regulated by the sun through the visual system and have a profound effect on our health and well-being.

The sleep

Sleep and dreams: mysterious, even mystical for some people, are one of the favorite topics of art and literature, philosophy and science. We have limited control over the decision to sleep, we can postpone sleep for a while but in the end we are overwhelmed by it. We spend about a third of our lives sleeping, and a quarter of that time in an active dream state.

Sleep is universal among the most advanced vertebrates. Prolonged sleep deprivation is devastating for proper psycho-physiological functioning.

Circadian rhythms

The majority of terrestrial animals coordinate their behaviour on the basis of circadian rhythms, the daily cycles of light and darkness that result from the rotation of the earth. The precise organization of circadian rhythms varies between species: some animals are active during the daytime hours, others only at night and the majority during transition times (from sunrise to dusk). Many physiological and biochemical processes in the body increase and decrease with daily rhythms: body temperature, blood flow, urine production, hormone levels, hair growth and metabolic rhythms have similar fluctuations.

When the cycles of light and darkness are removed from an animal's environment, the circadian rhythms do not change their organization because the clocks of circadian rhythms have no astronomical basis (the sun and the earth), but are the result of biological factors in the brain. External stimuli such as light and dark, or daily temperature changes, help to adjust the brain's clocks to keep them synchronized with the coming and going of natural sunlight.

The importance of sleep

Sleep is as important to our health as eating, drinking and breathing. It allows our bodies to repair themselves and our brains to consolidate our memories and process information. Poor sleep is linked to physical problems such as a weakened immune system and mental health problems such as anxiety and depression.

There are many factors impacting on your “good sleep", such as adjusting the light, noise and temperature in the bedroom, your eating, drinking and exercise habits and how you manage stress, and your environment. 

Sleep is very important for our immune system and for a more general and fundamental psychophysical balance for a healthy and happy life.

Some curiosities about sleep

1. All mammals, birds and reptiles sleep, although only mammals and some birds have REM stage.
2. The sleep period is very variable, from about 18 hours in bats and possums to about 3 hours in horses and giraffes.
3. Bottlenose dolphins sleep with only one brain hemisphere at a time, about two hours of sleep with one hemisphere, then one hour awake with both hemispheres, 2 hours of sleep with the other hemisphere and so on, for a total of 12 hours per night.
4. In 1963 Randy Gardner, then a high school student, broke the world record for continued waking: 11 days (264 hours) without sleep.

Sources:

1. Wikipedia
2. World Sleep Day World Association of Sleep Medicine
3. Why the sleep industry is keeping us awake at night". Guardian. 9 March 2019. Retrieved 21 April 2019.
4. Neuroscienze, esplorando il cervello. Bear, Connor, Paradiso