Sleep Difficulties - What Causes Fatigue: Chronic Fatigue

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Sleep difficulties

Difficulty getting a good night's sleep is a significant cause of tiredness in particular and fatigue in general. Lack of sleep isn't the only problem: Too little or too much sleep can increase your perception of fatigue, as can poor-quality sleep. Even if you get enough hours of sleep, you'll probably find yourself dragging more than usual the next day if that sleep was interrupted by frequent awakenings or lacked an important part of its nightly architecture of brain waves. (To determine the quality of your sleep, see "A sample sleep history questionnaire," below.)

Although sleep requirements vary, most people need eight hours a night to feel refreshed during the day. It's not surprising that getting less than you need leaves you feeling tired, but getting more than you need can be just as bad. Many people are surprised to find that on days when they sleep late in the morning, they don't feel more rested and recharged; indeed, they may feel more lethargic and unmotivated than usual.

The connection between too much sleep and too little energy has been borne out in experiments. When volunteers slept longer than usual, they reported feeling more fatigued. It appears that any significant deviation from normal sleep patterns can upset circadian rhythms and increase daytime fatigue. The best solution is to figure out how many hours of sleep are right for you and then stick with it — even on weekends and vacations.

Just as important as the duration of sleep is its quality. A good night's sleep has a particular architecture comprising two alternating types of sleep, marked by distinct brain-wave patterns. In rapid eye movement (REM) sleep, the eyes dart back and forth, and the brain races and dreams. The other type is non-REM sleep, or quiet sleep, which includes deep sleep, when blood pressure falls and the pulse rate slows by 20%–30%. While both states of sleep are important for restoring the body's energy, sleep researchers believe that deep sleep plays the biggest role. In an experiment from the 1970s in which volunteers had their sleep interrupted briefly, everyone felt somewhat fatigued the next day, but those who were awakened during deep sleep felt the most fatigued.

Unfortunately, most people don't get a good night's sleep. Either their sleep time is too short, or it's long enough but of poor quality. For example, they may sleep for four hours, lie awake, then sleep for four more hours, but not get enough deep, non-REM sleep.

Many lifestyle habits, foods, or even illnesses can interfere with the duration and quality of your sleep. Among the most common causes of sleep difficulties are these:

Caffeine. As a stimulant, caffeine interferes with adenosine, a neurotransmitter that promotes sleep. Caffeine can also interrupt sleep by increasing the need to urinate during the night. For some people, a single cup of coffee in the morning means a sleepless night because its stimulant effect is unusually long-lasting. For most people, the best recommendation is to avoid caffeinated beverages after midafternoon (see "Nutritional factors").

Alcohol. Although alcohol depresses the nervous system and therefore can help people fall asleep, it also has a stimulant effect several hours later. A drink before bedtime may make it easier to fall asleep, but it may cause you to awaken more easily and to spend less time in deep sleep (see "Alcohol").

Smoking. Nicotine is a central nervous system stimulant that can cause insomnia. It speeds the heart rate, raises blood pressure, and causes the mind to race. Even after getting to sleep, a smoker can be awakened in the middle of the night by the craving for nicotine.

Sleep disorders. Perhaps the best-known sleep disorder is insomnia, a condition in which you have trouble falling asleep, or wake up and find it difficult to get back to sleep. Another sleep dis­order is sleep apnea, in which people stop breathing momentarily during sleep. People with sleep apnea stop breathing as many as hundreds of times a night and wake up each time. The repeated interruption of sleep can cause drowsiness during the day. About 18 million Americans suffer from the disorder, and it's most common among those who are overweight.

Menopause. Hormonal changes that occur at menopause may interfere with sleep (see "Menopause").

Lack of exercise. The amount of deep, non-REM sleep that you get declines with age, but the decline is steepest in people who lead a sedentary life. Exercise is the only known way for healthy adults to boost their amount of deep sleep. Another benefit of aerobic exercise, in particular, is that it promotes restfulness by shortening the time it takes to fall asleep and reducing the frequency of nighttime awakenings (see "Inactivity").

If for any reason you aren't getting your share of sleep, you needn't suffer in silence or fumble about in a fog of fatigue. The first step is to make lifestyle changes such as cutting back on caffeine and alcohol and boosting your physical activity. If these steps don't work, see a doctor for advice about other options, including medications.

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Last updated:	January 23, 2007