All life on earth is built around circadian rhythm, which is impacted by multiple external causes, including daylight.
Circadian rhythm is often referred to as the body’s internal clock, influencing mental, behavioural and physical changes that happen roughly every 24 hours. These changes are controlled by the suprachiasmatic nucleus (SCN), which is located in the hypothalamus, where the light travels along the optic nerve to the SCN and signals the pineal gland to control levels of the hormone melatonin. Melatonin helps to regulate sleep cycles and plays a critical role in when we fall asleep and when we wake up. It is also an antioxidant, anti-aging, and helps to support the immune system.
A good night’s sleep is broken down between Non Rapid Eye Movement (stage one to three, non-REM), which accounts for up to 75 per cent of sleep, and Rapid Eye Movement (stage four, REM), which accounts for the other 25 per cent. Each sleep cycle is approximately 90 minutes long, which translates into roughly five cycles per night based on the average seven to nine hours sleep. REM sleep is often characterised as ‘active sleep’, when the brain activity is much faster and more similar to waking hours, whereas, non-REM sleep is more peaceful, with hardly any eye movement compared to faster eye movement during REM sleep.