WHAT MAKES YOU SLEEP?
Although you may put off going to sleep in order to squeeze more activities into your day, eventually your need for sleep becomes overwhelming. This need appears to be due, in part, to two substances your body produces. One substance, called adenosine, builds up in your blood while you’re awake. Then, while you sleep, your body breaks down the adenosine. Levels of this substance in your body may help trigger sleep when needed.
A buildup of adenosine and many other complex factors might explain why, after several nights of less than optimal amounts of sleep, you build up a sleep debt. This may cause you to sleep longer than normal or at unplanned times during the day. Because of your body’s internal processes, you can’t adapt to getting less sleep than your body needs. Eventually, a lack of sleep catches up with you.
The other substance that helps make you sleep is a hormone called melatonin. This hormone makes you naturally feel sleepy at night. It is part of your internal “biological clock,” which controls when you feel sleepy and your sleep patterns. Your biological clock is a small bundle of cells in your brain that works throughout the day and night. Internal and external environmental cues, such as light signals received through your eyes, control these cells. Your biological clock triggers your body to produce melatonin, which helps prepare your brain and body for sleep. As melatonin is released, you’ll feel increasingly drowsy. Because of your biological clock, you naturally feel the most tired between midnight and 7 a.m. You also may feel mildly sleepy in the afternoon between 1 p.m. and 4 p.m. when another increase in melatonin occurs in your body.
Your biological clock makes you the most alert during daylight hours and the least alert during the early morning hours. Consequently, most people do their best work during the day. Our 24/7 society, however, demands that some people work at night. Nearly one-quarter of all workers work shifts that are not during the daytime, and more than two-thirds of these workers have problem sleepiness and/or difficulty sleeping. Because their work schedules are at odds with powerful sleep-regulating cues like sunlight, night shift workers often find themselves drowsy at work, and they have difficulty falling or staying asleep during the daylight hours when their work schedules require them to sleep.
The fatigue experienced by night shift workers can be dangerous. Major industrial accidents—such as the Three Mile Island and Chernobyl nuclear power plant accidents and the Exxon Valdez oil spill—have been caused, in part, by mistakes made by overly tired workers on the night shift or an extended shift.
Night shift workers also are at greater risk of being in car crashes when they drive home from work during the early morning hours, because the biological clock is not sending out an alerting signal. One study found that one-fifth of night shift workers had a car crash or a near miss in the preceding year because of sleepiness on the drive home from work. Night shift workers are also more likely to have physical problems, such as heart disease, digestive troubles, and infertility, as well as emotional problems. All of these problems may be related, at least in part, to the workers’ chronic sleepiness, possibly because their biological clocks are not in tune with their work schedules. See “Working the Night Shift” for some helpful tips if you work a night shift.
Other factors also can influence your need for sleep, including your immune system’s production of hormones called cytokines. Cytokines are made to help the immune system fight certain infections or chronic inflammation and may prompt you to sleep more than usual. The extra sleep may help you conserve the resources needed to fight the infection. Recent studies confirm that being well rested improves the body’s responses to infection.
People are creatures of habit, and one of the hardest habits to break is the natural wake and sleep cycle. Together, a number of physiological factors help you sleep and wake up at the same times each day.
Consequently, you may have a hard time adjusting when you travel across time zones. The light cues outside and the clocks in your new location may tell you it is 8 a.m. and you should be active, but your body is telling you it is more like 4 a.m. and you should sleep. The end result is jet lag—sleepiness during the day, difficulty falling or staying asleep at night, poor concentration, confusion, nausea, and generally feeling unwell and irritable. See “Dealing With Jet Lag”.
Working the Night Shift
Try to limit night shift work, if that is possible. If you must work
the night shift, the following tips may help you:
Increase your total amount of sleep by adding naps and lengthening the amount of time you allot for sleep.
Use bright lights in your workplace.
Minimize the number of shift changes so that your body’s biological clock has a longer time to adjust to a nighttime work schedule.
Get rid of sound and light distractions in your bedroom during your daytime sleep.
Use caffeine only during the first part of your shift to promote alertness at night.
If you are unable to fall asleep during the day, and all else fails, talk with your doctor to see whether it would be wise for you to use prescribed, short-acting sleeping pills to help you sleep during the day.
Dealing With Jet Lag
Be aware that adjusting to a new time zone may take several days. If you are going to be away for just a few days, it may be better to stick to your original sleep and wake times as much as possible, rather than adjusting your biological clock too many times in rapid succession.
Eastward travel generally causes more severe jet lag than westward travel because traveling east requires you to shorten the day, and your biological clock is better able to adjust to a longer day than a shorter day. Fortunately for globetrotters, a few preventive measures and adjustments seem to help some people relieve jet lag, particularly when they are going to spend more than a few days at their destination:
Adjust your biological clock. During the 2–3 days prior to a long trip, get adequate sleep. You can make minor changes to your sleep schedule. For example, if you are traveling west, delay your bed time and wake time progressively by 20- to 30-minute intervals. If you are traveling east, advance your wake time by 10 to 15 minutes a day for a few days and try to advance your bed time. Decreasing light exposure at bedtime and increasing light exposure at wake time can help you make these adjustments. When you arrive at your destination, spend a lot of time outdoors so your body gets the light cues it needs to adjust to the new time zone. Take a couple of short 10–15 minute catnaps if you feel tired, but do not take long naps during the day.
Avoid alcohol and caffeine. Although it may be tempting to drink alcohol to relieve the stress of travel and make it easier to fall asleep, you’re more likely to sleep lighter and wake up in the middle of the night when the effects of the alcohol wear off. Caffeine can help keep you awake longer, but caffeine also can make it harder for you to fall asleep if its effects haven’t worn off by the time you are ready to go to bed. Therefore, it’s best to use caffeine only during the morning and not during the afternoon.
What about melatonin? Your body produces this hormone that may cause some drowsiness and cues the brain and body that it is time to fall asleep. Melatonin builds up in your body during the early evening and into the first 2 hours of your sleep period, and then its release stops in the middle of the night.
Melatonin is available as an over-the-counter supplement. Because melatonin is considered safe when used over a period of days or weeks and seems to help people feel sleepy, it has been suggested as a treatment for jet lag. But melatonin’s effectiveness is controversial, and its safety when used over a prolonged period is unclear. Some studies find that taking melatonin supplements before bedtime for several days after arrival in a new time zone can make it easier to fall asleep at the proper time. Other studies find that melatonin does not help relieve jet lag.
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