What are the real benefits of sleep on our health? A good night’s sleep. We can agree that a good night’s sleep not only refreshes and repairs but can we really say how? Let’s take a look at the benefits of sleep on the human body and brain to try and explain the science behind the seemingly magical panacea of a good night’s sleep.
Sleep benefits: A restorative function
One of the oldest hypothesis on sleep benefits is based on the replenishing of energy stocks. Every cell needs energy to function. This is particularly true of neurons, which alone account for 20% of the body’s total energy consumption. This energy is carried by the chemical bond of a small molecule called ATP (adenosine triphosphate). When needed, it fuels the energy-consuming cellular reactions, transforms into adenosine diphosphate (ADP). It is then regenerated to ATP through the degradation of different large energy-rich molecules: creatine in muscles, glycogen in the brain and so on.
But this regeneration is relatively slow. During awakening, the activity of our neuronal cells is intense. They consume ATP faster than it can be regenerated. Gradually, as the day moves along, the available energy resources decrease. In parallel, ADP accumulates in the brain and this accumulation increases the need for sleep, pushing us to go to bed. A sign telling us that it’s time to clean the circuits and refuel!
Sleep benefits: Spring cleaning
A more recent hypothesis is that sleep is the “cleansing” phase of the brain. Like any cell, the neuron carries out biochemical reactions. It degrades large molecules into smaller molecules of interest, creating “cellular waste”. During the day, high neuronal activity will tend to cause these co-products to accumulate in the neuron and in the fluid in which it bathes. Since neurons are very sensitive to the quality of their environment, some of these wastes may have toxic effects.
A system of channels will drain them out of the central nervous system, but this process is very slow. In 2013, an American research team showed that this cleansing process accelerated during sleep due to a 60% increase in spaces between neurons. The restorative aspect of sleep could, therefore, be the consequence of this greater elimination of the neurotoxic products, ensuring the preservation of the integrity and the good functioning of the brain cells.
Sleep benefits: Immunity
Knowledge of sleep function can also be drawn from observing the consequences of sleep deprivation. One of the earliest discoveries and one of the most widely accepted by specialists is the crucial role of sleep in immunity. In fact, you may have already experienced this- when you sleep too little, you are more likely to get sick.
A scientific study has proved it by exposing healthy humans to a rhinovirus, responsible for rhinopharyngitis, the common cold. The volunteers who slept less than 5–6 hours the following night were more likely to “catch a cold” than those who had a good night’s sleep. What’s more in hepatitis B vaccination test, subjects who had not slept sufficiently produced lower amounts of antibody.
Sleep benefits: Recovery
When we’re sick, we want nothing more that to get into bed and spend the whole day sleeping. No need to resist or feel guilty, by sleeping you are in fact helping your body get better! Cytokines, the molecules secreted by your immune system to fight the viral or bacterial invader, act like natural sleeping pills.
Cytokines cause an increase and an intensification of your slow, non-REM sleep. This in turn decreases the amount of energy necessary for your body and especially your brain. This energy can be preserved to help the body recover, or spent to cause a fever that will help fight the infection. But nothing in this function justifies the need for loss of consciousness related to sleep. So it’s probably an opportunistic function.
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