Sleep Stages

During the night, the body goes through several stages of sleep. The first four stages of sleep are non-REM (rapid eye movement) sleep. Stage 1 is the lightest sleep stage and the time when a sleeper can easily be awakened. Muscle activity and eye movement slows. Some people may experience a sensation of falling followed by sudden muscle contractions, like a startled “jumping.” In stage 2 (onset of sleep), eye movements stop and body temperature drops. Brain waves slow, but there are occasional bursts of brain activity. Stage 3 starts deep sleep. Brain waves are very slow, but there are still occasional smaller and faster brain waves. Deep sleep continues in stage 4, which is characterized by extremely slow brain waves. It is very difficult to wake someone from stage 3 or stage 4 sleep. If a person wakes up during these stages, he/she will feel very groggy and disoriented.

The final stage of sleep is REM (rapid eye movement) sleep. This is the time of active dreaming. As the name of the cycle suggests, the eyes move back and forth very rapidly. Breathing becomes rapid, shallow and irregular. Heart rate and blood pressure increase. The muscles in the arms and legs are temporarily paralyzed.

A single sleep cycle lasts from about 90 to 110 minutes and sleepers pass through several cycles during the night. The first REM sleep occurs about 90 minutes after falling asleep. As the night goes on, REM sleep periods increase in length and deep sleep periods decrease.

Sleep Needs

Sleep is needed to refresh the body and enable the brain to process and retain information. Lack of sleep can contribute to daytime mood problems, decreased productivity and an increased risk for accidents. Studies show an accumulated sleep “debt” may lead to the development of high blood pressure, obesity, cardiovascular disease and an increased risk for infections.

On average, adults need 7 to 9 hours of sleep each night. But surveys by the National Sleep Foundation find many Americans aren’t getting enough sleep. On average, respondents say they get 6 hours, 40 minutes of sleep on weeknights and 7 hours, 7 minutes on weekends. Twenty percent of Americans are getting less than six hours of sleep a night.

Coping with Sleepiness – Napping on the Job

Americans use several methods to combat daytime sleepiness. About 52 percent use exercise to keep up energy levels and stay awake. Nearly 60 percent use caffeinated beverages (like coffee, soda or tea). More than 40 percent pump up their energy levels by eating foods high in sugar or carbohydrates.

Roughly 53 percent of Americans combat daytime sleepiness by taking a nap. Sara Mednick, Ph.D., Research Scientist with the University of California San Diego, says that although nap time is typically allotted to babies and small children, it’s not a bad idea for adults. Most people have a natural tendency to become sleepy in the mid-afternoon (between 1:00 PM and 4:00 PM). Taking a nap can help the body cope with this need for sleep and reduce some of the sleep deficit many people have accumulated. Naps also improve performance better than caffeine.

Mednick says the ultimate nap should last about 90 minutes to allow the body to complete a sleep cycle. This can help improve memory and motor learning and increase alertness and creativity. People who can’t get in a 90-minute nap should aim for shorter naps (roughly 20 minutes) to reduce fatigue and fend off sleepiness. For workers, short naps can also increase productivity. But Mednick cautions that short naps shouldn’t exceed 20 minutes because nappers will go into deeper stages of slow-wave sleep and feel tired and groggy when they wake up.

Naptime Tips

Mednick says naps are most refreshing when they can be taken without disruption or distractions. Here are some of her suggestions: • Find a quiet place where you won’t have any interruptions. Mednick says many workers sneak in naps by taking a quick snooze in their cars. • If you have an office, turn down the lights and close the blinds to darken the room and induce sleep. An eye mask can also be useful to reduce light levels. • Use earplugs to eliminate distracting noise. • Set an alarm to vibrate so you aren’t startled by a sudden, loud noise. • Cover with a blanket. Your body temperature goes down when you rest, so you may get cold during the nap. • Keep a regular nap schedule. Your body will get used to powering down at a certain time of the day, making napping more efficient.

For information on sleep needs and napping: The Better Sleep Council National Institute of Neurological Disorders and Stroke National Sleep Foundation