The Good Sleep Series: Part 2

How Sleep Promotes Vitality

Fun Fact: An individual who lives until the age of 79 spends roughly 26 years of their life sleeping, and about 7 years trying to get to sleep. 33 years is well over a third of your life! And that is exactly what you need to function at an optimal level.

Getting enough rest is as important as the activities that you do to thrive and stay alive when you are awake. The human body is like a very complex machine, with multiple interrelated components that are constantly at work. Good sleep plays an important role in recharging and booting your operating system — kinda like how a phone needs to be charged after a few hours of use. 

The phenomena of sleep is very complex and dynamic. But the main goal is to maintain a healthy ‘Circadian Rhythm’. This is the body’s natural daily rhythm or internal clock. It occurs in varying patterns of wakefulness and sleep in a 24 hour cycle. These ‘sleep-wake’ cycles are controlled by certain parts of the brain, and are synchronised with environmental cues (light, temperature, time of the day, etc.). The circadian rhythms work in tandem with the body’s homeostatic systems to determine when you fall asleep and wake up, and regulate a wide range of physical and mental activity. Here are some awesome and specific physiological processes that take place during sleep.

Cardiovascular Function:

Snoozing is essential for your heart and body to recuperate and recover from strain. During this time, your heart rate slows down to about 20% – 30% below the waking rate and blood pressure (BP) falls. There is a strong correlation between elevated nighttime blood pressure and overall hypertension. Nocturnal high BP is highest in middle-aged adults, who work long hours in high-pressure jobs. Stress and lack of sleep are more predictive of coronary heart disease, heart failure, stroke and kidney disease.

Immunological Responses:

Sleep and the circadian system are important regulators of the immunity process, through a feedback loop between nerves, hormones and cytokines. The most immediate effector immune functions are at their peak during the wake period; while a slower but significant adaptive immune response is initiated during nocturnal sleep. This means that your body kicks into a pro-inflammatory phase (which allows the body to develop immunological memory) during sleep. During this phase, inflammatory immune cells like leukocytes/white blood cells increase in number, and hormones like ‘growth’ hormone and prolactin stimulate tissue growth and muscle repair.

Hormone Regulation:

There are several hormones that fluctuate and are metabolised based on the circadian rhythm, and synchronicity of sleep, nutrition and general behavior.

• Melatonin is the sleep hormone, which regulates the circadian rhythm and kickstarts the transition to sleep. It is naturally occurring and is released into the bloodstream is prompted by darkness. Your body releases more of it at night and suppresses it during the day. 
• Cortisol is usually more elevated during the first hour of wake period to keep you alert, and declines gradually during the day until nadir. Elevated levels of cortisol are associated with sleep disturbance and chronic insomnia, depression and stress-related disorders.
• Leptin and ghrelin are the ‘hunger hormones’, and have a major influence on energy levels. Leptin is a mediator of long-term regulation of energy balance, suppressing food intake and thereby inducing weight loss. Ghrelin on the other hand is a fast-acting hormone, which promotes appetite and food intake. Sleep deprivation increases ghrelin levels, while at the same time lowers leptin levels in the blood. This is closely associated with weight gain and obesity. 
• Insulin sensitivity is reduced by sleep deprivation and partial sleep, and this impacts the breakdown of glucose. Blood sugar/glucose levels are naturally higher during sleep, however the time of day and amount of sleep a person sleeps impacts insulin and cortisol levels, both of which affect glucose. Hitting the hay could lower unhealthy blood sugar levels by promoting healthy systems. Obesity and diabetes are affected by blood sugar levels, while one’s blood sugar also impacts obesity and diabetes. 
• Growth hormone for cell reproduction and regeneration.
• Antidiuretic Hormone, Aldosterone and Prolactin for water and electrolyte balance etc. 

Getting enough sleep is far from overrated

There are so many other short-term and long-term consequences of reduced or inadequate rest. It is evident that the body needs to be well rested for many significant physiological processes which enhance healing, restoration and recharging. In the next part of this series, we will cover different types of sleep disorders, and how to identify them.