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Why Can I Sleep?

Ability to Sleep Dependent on Multiple Factors

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Updated May 26, 2012

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

It may not bother you, but being able to sleep may have unexpected social consequences. You might get dirty looks from a bed partner at your ease of sleeping. Excessive daytime sleepiness may lead to naps and other consequences. Most people complain if they can’t sleep, typically unable to stay or fall asleep (a condition called insomnia), but what if you are able to sleep too easily? You may ask yourself: Why can I sleep?

The Biology of Sleep

First, you should recognize that your ability to sleep is dependent on multiple factors. Everyone needs to sleep, but not everyone needs to sleep the same amount or at the same time.

The amount of sleep that we need to feel rested seems to be written in our genes. This genetically determined sleep need serves as the foundation for our ability to sleep. Most people need an average of 8 hours of sleep, but some people can feel rested after routinely getting 6 hours of sleep and just as many may need 10 hours.

Getting less sleep than your body needs will result in sleep deprivation. This can have serious, and even fatal, consequences. Therefore, you might be able to sleep more (or more easily) because your body dictates that you need it. This isn’t a marker of laziness, but rather a need that is beyond your control. If you don’t meet your sleep needs due to sleep restriction, you will find that it becomes even easier to sleep.

Our sleep needs also change subtly during our lifetime. The sleep patterns of children vary markedly from those of adults. Moreover, as we age, our sleep may change again. We might fall asleep and awaken earlier, and our sleep generally will become more fragmented and we may feel that we are sleeping less soundly.

Beyond the ability to sleep that is determined by our genes and our station in life, there is variation in our ability to sleep during the day and night. After awakening, we accumulate a need to sleep that builds during the period that we remain awake. This is called the homeostatic sleep drive. In addition, our body follows a pattern of sleep and wakefulness called the circadian rhythm. This encourages us to sleep at night and remain awake during the day.

Some people have variation in their circadian rhythm. As an example, teenagers often have delayed sleep phase syndrome, which consists of a shift to a later desired bedtime and wake time. This circadian timing might also predispose you to an ability to sleep. You might notice this becomes evident after long trips that provoke jet lag, when you continue to desire to sleep according to your home’s time zone.

The Behavior of Sleep

Aside from your predetermined ability to sleep as described above, there is also a huge role for behavior in sleep. Although our behavior and choices may be influenced by our genetics, there is a considerable influence by our environment and even our culture.

The choices that you make during the day may help you sleep easily or keep you awake at night. As a result, many recommendations to improve our sleep at night encourage behaviors that will facilitate a good night's sleep. This is sometimes referred to as sleep hygiene. Much like dental hygiene helps to keep our teeth and gums healthy, observing good sleep hygiene rewards us with a healthful night of sleep.

Conversely, there are clearly poor choices that you might make that may ruin your sleep. As an example, a large cup of coffee right before bed may set you on edge and keep you awake. Choosing to keep a television blaring as you attempt to doze off may likewise be disruptive. The choices we make while awake may profoundly impact our sleep.

Therefore, no matter how well (or poorly) you can sleep based on your underlying ability, there is also a role for the behavior and choices you make as well.

When the Ability to Sleep Becomes a Problem

Nevertheless, your ability to sleep may represent a problem. If you suffer from excessive daytime sleepiness, despite adequate sleep to meet your needs, this may suggest a sleep disorder. The Epworth scale is often used to screen people for their level of sleepiness and to identify those who may be too sleepy.

Naps during the day may suggest that you are not meeting your sleep needs overnight. (It should be acknowledged that many societies both tolerate and encourage these daytime rest periods.) There are other conditions that might cause you to sleep too much. Sleep disorders, such as sleep apnea and restless legs syndrome, may disrupt our nighttime sleep. Other conditions, such as narcolepsy and idiopathic hypersomnia, may lead to excessive daytime sleepiness.

Our ability to sleep, even why we sleep, is a fascinating thing to consider. We should acknowledge that people’s ability to sleep varies. Someone may struggle with insomnia while another person, on the very next pillow, drops off to slumber without a second thought. There is also a clear role for behaviors and choices that affect our sleep. This variation is not necessarily a problem unless it interferes with our ability to function in our daily lives.

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