How Much Sleep Is "Enough"?
February 19, 2015
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By Dr. Mercola
If you’re like most people, you’re probably not sleeping enough, and the consequences go far beyond just feeling tired and sluggish the next day.
According to a 2013 Gallup poll,1 40 percent of American adults get six hours or less per night. Even children are becoming sleep deprived. According to the 2014 Sleep in America Poll,2 58 percent of teens average only seven hours of sleep or less.
Even the Centers for Disease Control and Prevention (CDC) has stated that lack of sleep is a public health epidemic, noting that insufficient sleep has been linked to a wide variety of health problems.
For example, getting less than five hours of sleep per night may double your risk of heart disease, heart attack, and/or stroke. Research has also found a persistent link between lack of sleep and weight gain, insulin resistance, and diabetes.3,4
But while the risks of insufficient sleep are well-documented, there have been lingering questions about how much sleep is “enough,” and recommendations have shifted upward and downward over the years. On February 2, the National Sleep Foundation released updated guidelines5,6,7 to help clarify this question.
Updated Sleep Guidelines
Led by Harvard professor Charles Czeisler, the panel of experts reviewed more than 300 studies published between 2004 and 2014 to ascertain how many hours of sleep most people need in order to maintain their health. The recommendations they came up with are as follows:
As you can see, the general consensus is that from the time you enter your teenage years, you probably need right around eight hours of sleep on the average. According to the panel:
Age Group Recommended # of hours of sleep needed Newborns (0-3 months) 14-17 hours Infants (4-11 months) 12-15 hours Toddlers (1-2 years) 11-14 hours Preschoolers (3-5) 10-13 hours School-age children (6-13) 9-11 hours Teenagers (14-17) 8-10 hours Young adults (18-25) 7-9 hours Adults (26-64) 7-9 hours Seniors (65 and older) 7-8 hours
“Sleep durations outside the recommended range may be appropriate, but deviating far from the normal range is rare. Individuals who habitually sleep outside the normal range may be exhibiting signs or symptoms of serious health problems or, if done volitionally, may be compromising their health and well-being.”
Modern Technology Can Affect Your Sleep in Several Ways
Modern technology is in large part to blame for many peoples’ sleep problems, for several reasons, including the following:
- For starters, the exposure to excessive amounts of light from light bulbs and electronic gadgets at night hinders your brain from winding down for sleep by preventing the release of melatonin. (Melatonin levels naturally rise in response to darkness, which makes you feel sleepy.)
- Electromagnetic radiation can also have an adverse effect on your sleep even if it doesn’t involve visible light.
According to the 2014 Sleep in America Poll,8 53 percent of respondents who keep personal electronics turned off while sleeping rate their sleep as excellent, compared to just 27 percent of those who leave their devices on.
- Maintaining a natural rhythm of exposure to daylight during the day, and darkness at night, is an essential component of sleeping well. But not only are most people exposed to too much light after dark, they’re also getting insufficient amounts of natural daylight during the day.
Daytime exposure to bright sunlight is important because it serves as the major synchronizer of something called your master clock, which in turn influences other biological clocks throughout your body.
Even Daytime Use of Technology Can Significantly Prevent Sleep, Especially Among Teens
People now get one to two hours less sleep each night, on average, compared to 60 years ago.9 A primary reason for this is the proliferation of electronics, which also allows us to work (and play) later than ever before.
According to recent research, teens in particular may have difficulty falling asleep if they spend too much time using electronic devices—even if their use of technology is restricted to daytime hours! As reported by the Huffington Post:10
“The cumulative amount of screen time a teen gets throughout the day -- not just before bedtime -- affects how long they sleep, according to the study11...Boys spent more time using game consoles, while girls favored smartphones and MP3 music players, but regardless of the type of device, the effect on sleep was the same. The researchers found that:
‘One of the surprising aspects was the very clear dose-response associations,’ said the study's lead researcher Mari Hysing... ‘The longer their screen time, the shorter their sleep duration.’"
- Using an electronic device within one hour of bedtime resulted in spending more than an hour tossing and turning before falling asleep
- Using electronics for four hours during the day resulted in a 49 percent increased risk of needing more than one hour to fall asleep, compared to those who used electronics for less than four hours total
- Those who used any device for more than two hours per day were 20 percent more likely to need more than an hour to fall asleep, compared to those whose usage was less than two hours
- Those who spent more than two hours online were more than three times as likely to sleep less than five hours compared to their peers who spent less time online
Good Sleep in Middle Age May Benefit You in Your Senior Years
Another study12,13--which looked at sleep habits and mental functioning in later years—reviewed 50 years’ worth of sleep research, concluding that sleeping well in your middle-age years is an “investment” that pays dividends later. According to Michael Scullin, director of the Sleep Neuroscience and Cognition Laboratory at Baylor University in Texas: "We came across studies that showed that sleeping well in middle age predicted better mental functioning 28 years later.”
This seems like a reasonable conclusion when you consider the more immediate benefits of getting enough sleep. Accumulated over time, both hazards and benefits are likely to pay dividends or exact a toll... For example, recent research14,15,16 shows that lack of sleep can shrink your brain, which, of course, can have adverse long-term ramifications. Other research published in the journal Neurobiology of Aging17 suggests that people with chronic sleep problems may develop Alzheimer’s disease sooner than those who sleep well.
Researchers have also found18 that adding just one hour of sleep a night can boost your health rather drastically. Here, they set out to determine the health effects of sleeping 6.5 hours versus 7.5 hours a night. During the study, groups of volunteers slept either 6.5 hours or 7.5 hours a night for one week. They then swapped sleeping durations for another week, yielding quite significant results. For starters, the mental agility tasks became much more difficult for the participants when they got less sleep. Other studies have also linked sleep deprivation to decreased memory recall, difficulty processing information, and dampened decision-making skills.
Even a single night of poor sleep—meaning sleeping only four to six hours—can impact your ability to think clearly the next day. It's also known to decrease your problem solving ability. The researchers also noted that about 500 genes were impacted. When the participants cut their sleep from 7.5 to 6.5 hours, there were increases in activity in genes associated with inflammation, immune excitability, diabetes, cancer risk and stress. From the results of this study, it appears as though sleeping for an extra hour, if you’re regularly getting less than seven hours of sleep a night, may be a simple way to boost your health. It may even help protect and preserve brain function in the decades to come.
A Fitness Tracker Can Be a Helpful Tool to Get More Sleep
To optimize sleep, you need to make sure you’re going to bed early enough, because if you have to get up at 6:30am, you’re just not going to get enough sleep if you go to bed after midnight. Many fitness trackers can now track both daytime body movement and sleep, allowing you to get a better picture of how much sleep you’re actually getting. Chances are, you’re getting at least 30 minutes less shut-eye than you think, as most people do not fall asleep as soon as their head hits the pillow.
I recently detailed some of the benefits of fitness trackers in my article “The Year in Sleep.” Newer devices, like Jawbone’s UP3 that should be released sometime this year, can even tell you which activities led to your best sleep and what factors resulted in poor sleep. When I first started using a fitness tracker, I was striving to get eight hours of sleep, but my Jawbone UP typically recorded me at 7.5 to 7.75. I have since increased my sleep time, not just time in bed, but total sleep time to over eight hours per night. The fitness tracker helped me realize that unless I am asleep, not just in bed, but asleep by 10 pm, I simply won’t get my eight hours. Gradually I have been able to get myself to sleep by 9:30 pm.
How to Support Your Circadian Rhythm and Sleep Better for Optimal Health
Making small adjustments to your daily routine and sleeping area can go a long way to ensure uninterrupted, restful sleep and, thereby, better health. I suggest you read through my full set of 33 healthy sleep guidelines for all of the details, but to start, consider implementing the following key changes:
- Make sure you regularly get BRIGHT sun exposure during the day. Your pineal gland produces melatonin roughly in approximation to the contrast of bright sun exposure in the day and complete darkness at night. If you are in darkness all day long, it can't appreciate the difference and will not optimize your melatonin production. To help your circadian system to reset itself, make sure to get at least 10-15 minutes of morning sunlight. This will send a strong message to your internal clock that day has arrived, making it less likely to be confused by weaker light signals later on. Also aim for 30-60 minutes of outdoor light exposure in the middle of the day, in order to “anchor” your master clock rhythm. The ideal time to go outdoors is right around solar noon but any time during daylight hours is useful. A gadget that can be helpful in instances when you, for some reason, cannot get outside during the day is a blue-light emitter. Philips makes one called goLITE BLU.19 It’s a small light therapy device you can keep on your desk. Use it twice a day for about 15 minutes to help you anchor your circadian rhythm if you cannot get outdoors.
- Avoid watching TV or using your computer in the evening, at least an hour or so before going to bed. Once sun has set, avoid light as much as possible, to promote natural melatonin secretion, which helps you feel sleepy. Devices such as smartphones, TVs, and computers emit blue light, which tricks your brain into thinking it's still daytime. Normally, your brain starts secreting melatonin between 9 and 10 pm, and these devices emit light that may stifle that process and keep you from falling asleep.
Even the American Medical Association now states:20 “…nighttime electric light can disrupt circadian rhythms in humans and documents the rapidly advancing understanding from basic science of how disruption of circadian rhythmicity affects aspects of physiology with direct links to human health, such as cell cycle regulation, DNA damage response, and metabolism.”
- Be mindful of electromagnetic fields (EMFs) in your bedroom. EMFs can disrupt your pineal gland and its melatonin production, and may have other negative biological effects as well. A gauss meter is required if you want to measure EMF levels in various areas of your home. At minimum, move all electrical devices at least three feet away from your bed. Ideally, turn all devices off while you’re sleeping. You may also want to consider turning off your wireless router at night. You don’t need the Internet on when you are asleep.
- Sleep in darkness. Even a small amount of light in your bedroom can disrupt your body’s internal clock and your pineal gland's melatonin production. Even the glow from your clock radio could be interfering with your sleep, so cover your radio up at night or get rid of it altogether. You may want to cover your windows with drapes or blackout shades. A less expensive alternative is to use a sleep mask.
- Install a low-wattage yellow, orange, or red light bulb if you need a source of light for navigation at night. Light in these bandwidths does not shut down melatonin production in the way that white and blue bandwidth light does. Salt lamps are handy for this purpose. You can also download a free application called f.lux21 that automatically dims your monitor or screens.
- Keep the temperature in your bedroom below 70° Fahrenheit. Many people keep their homes too warm (particularly their upstairs bedrooms). Studies show that the optimal room temperature for sleep is between 60 to 68° F.
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- National Vaccine Information Center (NVIC) – A non-profit organization that seeks to prevent vaccine injuries and deaths through public education and defending your right of informed choice.
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- Fluoride Action Network (FAN) – An international coalition aimed at ending water fluoridation and alerting you to fluoride's environmental and health risks. FAN keeps you informed about fluoride toxicity, and monitors government actions that may expose you to fluoride.
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