Sleep is an essential function that allows your body and mind to recharge, leaving you refreshed and alert when you wake up 123. During sleep, your body undergoes various functions that contribute to overall health. The sleep cycle, including REM and non-REM stages, repeats several times throughout the night. Adequate sleep duration varies by age, but adults generally need at least 7 hours per night 1. Insufficient sleep can result in poor focus, reduced cognition, delayed reactions, mood swings, and a higher risk for illness 123.
The Science Behind Sleep An internal “body clock” regulates your sleep cycle, controlling when you feel tired and ready for bed or refreshed and alert. This clock operates on a 24-hour cycle known as the circadian rhythm. After waking up from sleep, you’ll become increasingly tired throughout the day. These feelings will peak in the evening leading up to bedtime.
This sleep drive – also known as sleep-wake homeostasis – may be linked to adenosine, an organic compound produced in the brain. Adenosine levels increase throughout the day as you become more tired, and then the body breaks down this compound during sleep. Light also influences the circadian rhythm. The brain contains a special region of nerve cells known as the hypothalamus, and a cluster of cells in the hypothalamus called the suprachiasmatic nucleus, which processes signals when the eyes are exposed to natural or artificial light.
These signals help the brain determine whether it is day or night. As natural light disappears in the evening, the body will release melatonin, a hormone that induces drowsiness. When the sun rises in the morning, the body will release the hormone known as cortisol that promotes energy and alertness 123.
