Sleep: A Health Priority
You might be surprised to find out that there is not a singular universally-accepted explanation for why we sleep. We all understand that we feel better when we get enough sleep and that we feel worse when we don’t get enough (or if the quality of our sleep is poor) so we know from first-hand experience that sleep is important–but why do we sleep instead of just being still with our eyes closed and resting? The experts at the National Sleep Foundation offer some theories to explain this question.
One theory is for energy conservation. Our metabolism slows down during sleep–our body temperature drops and we burn fewer calories. Some studies have shown that our metabolism drops as much as 10% during sleep as compared with sedentary wakefulness. So, maybe sleep is a way to systematically protect our energy supply.
Another theory is for restoration. Perhaps the reason for sleep is that it allows our bodies to repair and rejuvenate themselves. Animals completely deprived of sleep will lose all immune function in a matter of weeks and die. Some of the restorative functions that occur mostly during sleep include growth hormone release, tissue repair and muscle growth. Our brains also “clean house” during sleep by clearing adenosine, a by-product of brain cell activity. Adenosine levels remain high during wakefulness but are reduced during sleep. It is thought that the accumulation of adenosine over the course of the day is what kicks in the sense of sleepiness which promotes sleep.
A relatively new theory is that of brain plasticity. That is, certain changes take place in the brain during sleep which seem to affect how the brain functions when awake. Our ability to learn, remember and perform tasks is directly and significantly impacted by the amount and quality of sleep we get. Our mood and perception of events is also influenced by whether we get enough good sleep. During infancy and childhood, sleep is critical not only to how the brain functions but how it develops over time.
While none of these theories is considered the one definitive explanation for why we sleep, they all illustrate the importance of sleep and, therefore, all contribute to a better understanding of why we sleep.
The amount of sleep we each need varies depending on our age, activity level and health status. Generally speaking, the chart below outlines the range of hours required per age:
Recommended Amount of Sleep
|Newborns||16–18 hours a day|
|1-12 month old infants||14-15 hours a day|
|Preschool-aged children||11–12 hours a day|
|School-aged children||At least 10 hours a day|
|Teens||9–10 hours a day|
|Adults||7–8 hours a day|