A good night's sleep is invaluable - priceless, even - but so many people know the frustration of not being able to regularly sleep well. Not getting enough quality sleep can lead to many chronic diseases such as diabetes, obesity, dementia, and heart disease. Yes, sleep really is that important! There are many factors involved in sleeping well, and genetics plays a role in some sleep disorders. Looking at the genetic basis of sleep disorders may give you ideas on which path to take to fix the problem.
What is sleep and why do we need it?So this turns out to be a more difficult question to answer than you would think. We are asleep for about a third of our lives. All animals, both big and small, sleep. So you would think that scientists would know exactly why and how sleep works... Instead, we have almost as many questions about sleep as we have answers. Let's look at the definition of sleep from a prominent sleep medicine textbook: "Sleep is a recurring, reversible neuro-behavioral state of relative perceptual disengagement from and unresponsiveness to the environment. Sleep is typically accompanied (in humans) by postural recumbence, behavioral quiescence, and closed eyes."[ref] Yep - big words for laying down, closing your eyes, and going to sleep. The important thing here, though, is what goes on in the brain while you sleep. While your body is inactive (hopefully), your brain is doing some pretty cool and weird stuff while you sleep. And there are different metabolic processes going on in your body while you are asleep.
Why is sleep so important?While you sleep, your brain consolidates memories -- it makes the things that you learned during the day stick in your brain. This has been known for a long time and is something that researchers frequently experiment with.[ref] Recently, researchers experimented with just decreasing certain stages of sleep and showed that the neuroplastic changes to the brain in learning happen specifically during deep sleep.[ref] Studies of sleep deprivation show that there can be devastating consequences.
- In general, sleep deprivation causes a decrease in speed and accuracy in tests for attention, working memory, processing speed, short-term memory, and reasoning. [ref]
- One-third of accidents in a survey of commercial truck drivers were caused by drowsy driving due to sleep deprivation. [ref]
- According to the NTSB, going more than 20 hours without sleep is equivalent to driving legally drunk. And your risk of being in a car crash goes up 3-fold! [ref]
- This pretty much sums of the rest of the effects of sleep deprivation: 'studies have shown that short sleep duration is associated with an increased incidence of cardiovascular diseases, such as coronary artery disease, hypertension, arrhythmias, diabetes, and obesity, after adjustment for socioeconomic and demographic risk factors and comorbidities.' [ref]
Stages of sleep:When you sleep, your brain goes through different periods of activity. These are categorized into slow-wave sleep and REM (rapid eye movement) sleep. Slow-wave sleep can further be broken down into deeps sleep and lighter sleep. About 50% of sleep in adults is the light, non-REM sleep. Most of your deep sleep comes during the early part of the night, while the latter half of the night has much more REM sleep. [ref]
What causes you to feel sleepy?We feel the need to sleep each night due to two causes: our natural circadian rhythm and increased homeostatic sleep drive. The homeostatic sleep drive is what researchers call the build-up over the course of the day for the need to sleep. This is mainly driven by a build-up of adenosine in the brain, which is then cleared out during sleep. Adenosine is part of the ATP (adenosine triphosphate) molecule which is used for cellular energy. As you use energy over the course of the day, you build up adenosine in the brain. (Caffeine makes you feel more awake by blocking the adenosine receptors) [ref]
How do genetics affect sleep?
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