- How Sleep Works
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The short answer: adults need 6 to 9 hours per night. Around 7 to 7.5 hours of actual sleep (not counting time falling asleep and getting out bed) appears to be optimal for most people.
The long answer: it depends. The amount of sleep each person needs depends on many factors, including age, health, recent physical exertion, and mental activity. There is genetic influence, too. Some people just need more sleep than others and this runs in families.
The federal government’s Healthy People initiative has established a goal of getting more people to get adequate sleep on a regular basis. Their recommended amount of sleep is 8 hours for people 18 to 21 and 7 hours per night for adults over 21. According to their numbers, 69.6% of the population meets this goal, and the government wants to raise this to 70.9% by 2020.
The amount and type of sleep needed changes from childhood to adulthood.
|Age||Recommended amount of sleep|
|Infants under 1 year||16 to 20 hours|
|1-2 years old||14 hours|
|3-4 years old||12 hours|
|5-12 years old||10 hours|
|13-19 years old||9 hours|
|Adults & seniors||7 to 8 hours|
How much sleep do babies need? Infants sleep 16 to 20 hours each day. By age four, the amount of sleep required decreases to 12 hours. This sleep is spread out throughout the day. Once a child is six, they typically get most of their sleep during the night.
How much sleep does a teenager need? As children age, they require less sleep. By the time they reach adolescence, teenagers only need about 9 hours on average.
How much sleep does the average adult need? For most adults, 7 to 8 hours a night appears to be the best amount of sleep, although some people may need as few as 5 hours or as many as 10 hours of sleep each day.
How much sleep do seniors need? Sometimes you’ll hear that you need less sleep as you get older, but that is incorrect. A 2014 study revealed that seniors actually require similar amounts of sleep as younger adults, as much as 9 hours, although they only get 7.5 hours on average. The issue is that with age, the neurons responsible for regulating our sleep patterns slowly die off. This causes seniors to wake up even if they’re not fully rested, and to suffer from insomnia that makes it difficult to fall asleep in the first place.
While the required amount of sleep ranges for adults between 5 to 10 hours, you shouldn’t assume you are at one end of the spectrum unless you have paid close attention to your body. If you are drowsy during the day, even during boring periods, you haven’t had enough sleep the previous night. Most people experience a dip in early afternoon – siesta time. But if you fall asleep in the afternoons consistently, it means you haven’t had enough sleep at night.
If you’re American, chances are you aren’t getting enough sleep. A Gallup poll (2005) of Americans past age 50 found only 32% reported getting a good night’s sleep routinely. 56% said they got between 6 and 8 hours a night. The US Dept of Health and Human Services reports that “The odds of being a short sleeper (defined as someone who sleeps less than 6 hours a night) in the United States have increased significantly over the past 30 years.”
Sleep deprivation for even one or two nights can vastly affect your need for sleep. Unlike many things in life, sleep time is not something that is routinely changed. You can’t get used to a lower amount of sleep just because it fits your schedule. If you try to, it will affect your judgment and reaction time, even if you are not consciously aware of it. But you can’t resist it for long. Sleep deficit can be cured only by getting some sleep.
What happens when we miss sleep and then make it up? Even with free recovery, only one-third to one-half of lost sleep is recovered. All the lost deep sleep is recovered and about ½ of the REM sleep. Time spent in light sleep is lost.
If you routinely fall asleep within 5 minutes of lying down, you probably have sleep deprivation or a sleep disorder. Microsleeps, or very brief episodes of sleep in an otherwise awake person, are another mark of sleep deprivation. In many cases, people are not aware that they are experiencing microsleeps. Some suspect that the widespread practice of “burning the candle at both ends” among harried workaholics has changed perceptions so much that what is really abnormal sleepiness is now considered normal.
It is known that both long sleepers and short sleepers have higher mortality rates than people who sleep around the standard 8 hours. Sleep debt is also connected with higher rates of depression and weight gain, as well as poorer immune system and memory function.
Objective tests on healthy people show that depriving them of deep sleep negatively affects cognitive skills. People who suffer from insomnia get less deep sleep, and tend to subjectively equate this decline in deep sleep with an overall decline in sleep quality.
Seniors in particular are prone to insomnia. Some experts consider insomnia a normal part of aging, or it may result from medical problems that are common in elderly people and from the medications and other treatments for those problems.
Do people even know how much sleep they are getting? No. Unfortunately, individuals are notoriously inaccurate at estimating how much they slept, so you can’t necessarily believe what they report. Tests with actigraphy have found that in general people overestimate how much they sleep.
The best way to find out if you are getting enough sleep is to note the time when you go to bed and when you wake up. If you don’t have trouble falling asleep, you can assume it takes about 15 to 20 minutes for you to fall asleep. Add those 20 minutes to the time you went to bed, and then subtract from the time you wake up. Is it somewhere within the recommended range of 7-9 hours?
If it is, but you still don’t feel rested, here are signs you may need more or less sleep.
How do you know if you are over- or under-sleeping? Realistically, only if it impacts your daytime waking life.
There is usually no particular biological or health reason to worry about sleeping less or more than other people. Your spouse might get mad at you if you sleep too much and you might get into hot water if you nap on the job, but most people have no reason to worry about going outside the norms when it comes to sleep duration. You might think sleeping too much is a problem, that excessive sleep is a waste of time, and indeed hypersomnia is recognized as a clinical condition. But not all long sleepers can be classified as hypersomniac and in any cases, there is nothing doctors can do for hypersomnia except prescribe stimulants. So it may not be worth worrying about.
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