10 eye-opening facts about sleep
Sleep never fails to mystify people. It figures in every religion and mythology around the world and in the poetry of every language. Shakespeare has rightly been called the first sleep specialist because his works are so rich in sleepers, dreamers, insomniacs, and sleepwalkers, as well as lovely lyrical passages about sleep, such as this one spoken by Macbeth: “Sleep that knits up the ravell’d sleave of care, The death of each day’s life, sore labours bath, Balm of hurt minds, great nature’s second course, Chief nourisher in life’s feast.”
Today, despite decades of research, scientists still don’t understand exactly why we sleep and how it benefits us. The best guess is that it enables the brain and the rest of the central nervous system to work properly. The brain may need sleep to recover from the day’s work just as muscles do — “sore labours bath, balm of hurt minds,” as Shakespeare puts it. There is growing evidence for sleep as the partner of memory. In particular, it appears to strengthen newly formed memories and weed out old ones. But accumulating research shows that sleep affects nearly every bodily system — and that poor sleep can harm your health in many ways.
Here are 10 things you need to know about sleep:
1. Sleep is an activity that has a structure. It is not a simple process of falling asleep, snoozing soundly, then awakening later. Nobody sleeps “like a log.” It is not abnormal to wake briefly, even a few times a night and not remember it. You move in your sleep — muscles, eyes — and your heart rate and blood pressure vary.
Sleep consists of four stages, which you cycle through usually four to five times a night:
• Stage 1: Very light sleep. It normally makes up only five percent of your nightly sleep.
• Stage 2. Electrical activity in the brain slows. This accounts for about half of the total sleep time.
• Stage 3. Deep, restorative sleep. It features very slow brain waves, called delta waves. This stage makes up 25 percent of sleep and decreases with age.
• Stage 4. REM (rapid eye movement) sleep. This is when you dream; it accounts for about 20 percent of total sleep time.
2. The sleep/wake cycle is controlled largely by your brain’s biological clock, which also controls other daily rhythms, such as changes in body temperature, blood pressure, and the release of hormones. These are also known as circadian rhythms. A key player in this clockwork is the hormone melatonin, which is produced at night by the pineal gland in the brain and promotes drowsiness. Light, especially blue light from the sun, suppresses this “darkness hormone.” This is why one-way daylight contributes to alertness, and why darkness at night increases sleepiness. Habit can also have a powerful effect on the sleep/wake cycle. If you are used to falling asleep at 11 p.m., you will want to go to bed by then. Shift workers can get used to sleeping during the day or napping at odd hours, though this is difficult and unsatisfactory for most people and has been linked to health problems.
3. What is “enough” sleep? Enough sleep is whatever makes you feel refreshed and alert the next day. Most adults do best with six to eight hours — but for some, it’s nine or 10; for others, six or even less. How well you sleep is as important as how long. Though studies have linked the six-to-eight-hour range to lower death rates, what that means for individuals is unclear. What is most important is to get whatever is “enough” sleep for you.
4. Humans spend about a third of their lives sleeping — at least the lucky ones do. But many of us have insomnia, which simply means difficulty falling or staying asleep. Estimates vary, but perhaps one-quarter to one-third of all adults — and half of those over 65 — regularly suffer from insomnia, and nearly everybody has it at some time. In addition, some people choose to curtail their sleeping hours to squeeze in more time for work or play, while others are forced to do so by circumstances. In the US, for example, 60 percent of Americans say they get only a few good nights of sleep a week. You may have trouble falling asleep, staying asleep, or both. You may sleep well with the help of a sleeping pill. You may often fall asleep easily but wake up very early and not get back to sleep. Whatever the pattern or cause, inadequate sleep can make you feel exhausted all the time, adversely affecting your ability to work, think, and drive. And as accumulating research shows, chronic poor sleep can harm your physical and mental health.
5. Chronic poor sleep can cause or contribute to many serious health problems. Notably, sleep helps support the immune system. One week of poor sleep can lower resistance to infections and impair wound healing. Studies have also linked poor sleep to increased risk of hypertension, type 2 diabetes, stroke, heart attack, cognitive impairment, depression, anxiety disorders, and premature death. The risks posed by poor sleep are clearest when it is the result of obstructive sleep apnea, a growing problem.
6. Estimates vary, but it’s likely that sleep apnea affects about 10 percent of all adults. Rates have been steadily rising in the past 20 years, largely because of the obesity epidemic. Sleep apnea is caused by a temporary blockage of the throat’s breathing passages. The tongue and other soft tissues fall back, partially or totally blocking the airway. As a result, oxygen levels in the blood fall and carbon dioxide rises. Your throat muscles contract as you struggle for air, you gasp or snort loudly, then you start breathing again (because your brain wakes up briefly) and then fall back once again to sleep, until the cycle starts all over again. By robbing you of restorative sleep, apnea leads not only to daytime drowsiness, but also to irritability, faulty memory, inability to concentrate, headaches, and possibly depression and decreased libido. Especially dangerous: People with sleep apnea are at high risk for falling asleep while driving. It is known to increase the risk of heart disease, stroke, diabetes, depression, osteoporosis, glaucoma, and premature death. If it seems you may have sleep apnea, you should consult a sleep specialist. Among the usual treatments are losing weight and using a CPAP (continuous positive airway pressure) machine, which consists of an air pump attached to a mask via tubing, which is very effective at keeping your throat open during sleep. The devices have improved in recent years — less cumbersome, quieter, and less likely to cause claustrophobia.
7. Here’s what sleep experts recommend to improve your odds of getting a good night’s sleep: Finish eating at least two to three hours before your regular bedtime. Eat a healthful, balanced diet with a minimum of refined sugars, which are stimulating. Avoid nicotine. Avoid caffeine (coffee, tea, soft drinks, chocolate) close to bedtime. Avoid alcohol, which can lead to disrupted sleep during the night. Maintain a regular bedtime and wake time schedule. Establish a regular, relaxing bedtime routine. Avoid stimulating activities just before bedtime. Create a sleep-conducive environment that is dark, quiet, and not too cool or too warm, with comfortable mattress and pillows. Exercise regularly but complete your workout at least a few hours before bedtime. And lastly, use your bedroom only for sleep and sex. (However, reading in bed for relaxation is okay.)
8. There’s a wide variety of prescription sleeping pills on the market. They are generally effective and safe when used as directed, with a lot of caveats (read the package inserts thoroughly). These drugs are categorized as “controlled substances” for good reason, since dependency, tolerance, and abuse can occur. Precautions include: Take the lowest effective dose (Try halving the dose listed on the label). Don’t drink alcohol if you plan to take a sleeping pill since that increases the risk of side effects. Don’t take a sleeping pill if you are a pilot, firefighter, caretaker, or a health professional on call. Don’t drive a car or use machinery (such as power tools) if you feel groggy or hung over after taking a pill the night before. Even if you don’t feel groggy, consider not driving the next morning. Bottom line: There is no “best” sleeping pill. Your goal should be to sleep well without taking any sleeping pill!
9. Do you need less sleep as you get older? The answer is no. It is a myth that the older you get, the less sleep you need. You need as much as sleep as ever, but you sleep less soundly and you tend to fragment your sleep — that is, you wake up more often and for longer periods — and your deep sleep stages become shorter. While it’s commonly believed that almost all older people are poor sleepers, a large survey published in the journal Sleep in 2012 found that self-reported sleep actually improves with age, except for a worsening between ages 40 and 60. Unless medical or psychiatric problems interfere with their sleep, older people report fewer sleep disturbances and less daytime sleepiness than their younger counterparts.
10. Is it okay to have a siesta? What’s the optimal length? The urge to nap in the afternoon is nearly universal and is driven largely by our circadian rhythms. Most adults find that a short nap improves concentration and alertness. A growing body of research indicates that napping helps improve memory and learning. Here’s what to remember about siestas: Nap according to your own needs. Most people prefer short naps since long naps tend to leave them feeling groggy. Don’t nap close to your bedtime. And lastly, remember that taking a siesta is not for everyone. Some people find it hard to nap or feel worse after they do — and if they have insomnia, taking a siesta may worsen it!
Indeed, findings of recent studies have suggested that sufficient sleep “should now be mentioned as an additional way to reduce the risk of cardiovascular disease.” The evidence is certainly growing that chronic insufficient sleep should now be added to our list of health risk factors, such as poor nutrition, lack of exercise, stress, cigarette smoking, and excessive alcohol intake.
