Stages of Sleep
There are two states of sleep:
- Non-rapid eye movement (NREM) sleep
- Rapid eye movement (REM) sleep.
REM sleep is associated with dreaming. Your body muscles (except your eyes and lungs) do not move during this stage of sleep.
NREM sleep has four stages distinguishable by EEG waves.
REM sleep alternates with NREM sleep approximately every 90 minutes. A person with normal sleep usually has four to five cycles of REM and NREM sleep during a night.
Sleep disorders are conditions that affect a person's ability to get a restful night's sleep. Some of the most common examples are insomnia, restless legs syndrome, snoring, and sleep apnea.
As many as 70 million Americans are afflicted with sleep-related problems. While some sleep disturbances may be linked to biological changes associated with aging or certain physical diseases, especially those that cause pain, others may be associated with a mental health disorder such as depression or anxiety. Poor sleep may also stem from "bad" habits such as napping too long or too late in the day, or doing shift work. On the other hand, you may simply not be giving yourself the opportunity to acquire ample shuteye.
Disorders of sleeping and waking interfere with quality of life and personal health. Sleep is not just resting or taking a break from busy routines -- it is essential to physical and emotional health. Adequate sleep may also play a role in helping the body recover from illness and injury. Inadequate sleep over a period of time is associated with obesity, diabetes, heart disease, and depression.
But the emotional and mental benefits of sleep are also significant. Even occasional sleeping problems can make daily life feel more stressful and less productive. And some people with chronic insomnia are more likely to develop psychiatric problems. Those who have trouble getting sleep may also experience problems in memory, learning, logical reasoning, and mathematical calculation.
Insomnia -- the inability to fall asleep and remain there -- affects many millions of people. Sleep apnea affects an additional 10 million to 15 million. Narcolepsy (falling asleep uncontrollably during the day) affects around 200,000. About 5 percent of the population have restless legs syndrome.
While people of any age may be affected, there seems to be a large prevalence of sleep disturbances among older men and women. Sleep studies reveal that they get less REM (deep) sleep over time. With aging, sleep becomes more fragile; that is, it doesn't take much disturbance to awaken the individual. Women may first notice this during menopause.
Most sleep experts believe you should get seven to eight hours of sleep a night. This figure varies considerably across the age span and from person to person. Still, if you're getting less than six hours of sleep per night regularly, you may be compromising your health and welfare. If you have some of the following problems, you may need more sleep, or a better quality of sleep, than you are getting: trouble staying alert during boring or monotonous activities; tendency to be unreasonably irritable with co-workers, family, or friends; and difficulty concentrating or remembering facts.
If you're having chronic sleep difficulties, try practicing sensible sleep habits. If you've done all you can, however, and still aren't getting good, quality sleep, talk with your family doctor. If you need additional help, ask for a referral to a sleep specialist. This may be needed, in particular, for more complex conditions such as narcolepsy. While this disease is not curable, it is treatable, though the regimen with carefully prescribed medications is complicated, and best handled by a sleep specialist. On the other hand, sleep apnea treatment can be very helpful.