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Sleep Disorders

Specific times for best sleep



Is there a specific time which people should sleep, so that it will benefit the body the most? If so, could not sleeping at this time possibly affect a human`s emotions during the day (crankiness, grouchiness)?


Sleep varies between individuals, both in duration and in timing. However there are two general rules that apply to the majority of people.

The first rule is that the longer we are awake, the sleepier we get. This is called sleep pressure (or the homeostatic controller of sleep). Sleep pressure is easy to understand and its effects are the most predictable between the two sleep controllers. Getting enough sleep relieves the homeostatic pressure. The key word here is: enough sleep. If one does not get enough sleep, they will be sleepy during wake time.

The second sleep controller is the biological or internal clock (also called the circadian controller of sleep and wakefulness). The biological clock creates variability in our preferred time to fall asleep and the time we are most awake.

The role of the "internal clock" deserves further explanation. For example, an individual may find it easy to wake up at 5 or 6 in the morning and to fall asleep in the evening, while another individual's internal clock might be the opposite by waking them up in the evening and making them go to sleep in the early morning. These are two extreme examples; though in general people have a natural preference towards alertness either in the early morning or late at night (morning larks and night owls), or somewhere in between.

In order to make the most of sleep, we should take advantage of out natural circadian rhythm tendencies. You can answer these following few questions to calculate your natural tendency (the Morningness-Eveningness questionnaire is posted on the website); that is, whether you are a morning lark or a night owl, and therefore, the best time for you to sleep and the best time for you to be awake.

Going against your internal clock's tendency and choosing a different sleep and wake time than your natural preference can be detrimental to your mental and physical performance in the short term, causing symptoms similar to jet lag. These effects can range from disturbed sleep, impaired daytime alertness and performance, disorientation, gastrointestinal problems, and loss of appetite. These ill effects, luckily, are short term. They tend to resolve when the internal clock is re-set to the new schedule, granted that there is a regular schedule. This means the biological clock is capable of correcting itself according to environmental cues, like light, level of activity, and food intake. 

Re-setting your internal clock can be achieved, but may require help from a Sleep Specialist. Some of the tools to do this include strategic exposure to light, exercise, and judicious use of caffeine; and may require the supplementation of a naturally occurring substance called melatonin. Re-setting an internal clock often takes a whole day for every one hour shift in environmental cues.

If you would like additional information regarding sleep and sleep disorders, you can obtain it on the American Academy of Sleep Medicine website. This website also contains a list of Sleep Centers across the country so you can locate one near you if need it. I hope this was helpful. Good luck, and sleep well.

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Response by:

Ziad  Shaman, MD Ziad Shaman, MD
Assistant Professor of Medicine
School of Medicine
Case Western Reserve University