The Sleep Cycle and our Health

Sleep is far from the passive phenomenon of having a sole purpose of helping mind and body recover from day’s wear and tear. In fact, sleeping is a biological state just as complex and varied as our state of wakefulness. Unaware to us, our sleep state rotates through various stages throughout the night affecting everything from our heart and respiration rate to hormone secretion and body temperature. This is called the REM and non-REM cycle. There is also a bigger cycle that rotates between our awake and asleep state. The physiological changes that our body goes through each of these cycles play an immense role in maintaining our physical and mental health. The list of health disorders associated with a suboptimal sleep cycle include heart disease, diabetes, depression, indigestion, ulcers, aggressive behavior, slow reflexes, muscle fatigue and even hallucinations.

Our body is essentially a slave to its natural circadian rhythm, which in itself is a slave to Earth’s daily day and night cycle. There is a small collection of neural cell bodies in our brain called Suprachiasmatic nucleus (SCN)that is the origin of our circadian rhythm. The SCN has its own clock which is synced with the daylight, a information it receives from the retina. SCN has a role to play in production of two hormones, melatonin and cortisol, which in turn cause various cyclical changes in our body. Melatonin gets your body relaxed and ready to sleep. Cortisol on the other hands gets you energized for the day and your body ready to metabolize your breakfast. 

Every animal and plant has physiological changes that are a direct result of sunlight. The first threat to this cycle was humans gaining control of fire and then subsequently the era of electricity. Humans changed their lifestyle while our biological clocks are still helplessly tied to sunlight. This clock syncs to the highest luminosity around. Unfortunately, the artificial night lights are no where close to the luminosity of sunlight even while indoors. So, regardless of our night plans, our body is preparing for sleep. Requiring our body to divert energy towards us staying up is harmful. For example, staying up means we are likely to eat late. Such meals can’t be metabolized properly due to low cortisol, increasing blood cholestrol levels. Study has shown that people who work night shifts have a higher risk of heart disease.