In today's "24/7" society, many people cut back on sleep to squeeze in more time for work, family obligations, and other activities. But skimping on sleep can be harmful. A comprehensive new handbook from the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health (NIH) explains that sleep is not merely "down time" when the brain shuts off and the body rests.

"Our brains are very active during sleep, and research has shown that adequate sleep is important to our overall health, safety, and performance," notes Michael Twery, PhD, acting director of NHLBI's National Center on Sleep Disorders Research. "Scientists also have a better understanding of how a chronic lack of sleep or an untreated sleep disorder can impair health. Like good nutrition and physical activity, adequate sleep is critical for continued good health."

"Your Guide to Healthy Sleep" provides the latest science-based information about sleep in an easy-to-understand format. The 60-page handbook describes how and why we sleep, and offers tips for getting adequate sleep, such as sticking to a sleep schedule, relaxing before going to bed, and using daylight or bright light to help you adjust to jet lag and shift work schedules.

Sleep disorders such as insomnia (trouble falling asleep or staying asleep, or unrefreshing sleep), sleep apnea (brief periods of pauses in breathing or shallow breathing while you are sleeping), restless legs syndrome (an almost irresistible urge to move the legs that can make it difficult to fall asleep or stay asleep), and narcolepsy (excessive and overwhelming daytime sleepiness despite adequate nighttime sleep) are also described with information on diagnosis and treatment. In addition, a sample sleep diary helps readers track their sleep-related habits.

Sleep needs vary from person to person, and they change throughout the lifecycle. Newborns sleep between 16 and 18 hours a day, and children in preschool sleep between 10 and 12 hours a day. School-aged children and teens need at least 9 hours of sleep a day. Research suggests that adults — including seniors — need at least 7 to 8 hours of sleep each day to be well rested and to perform at their best.

Studies have linked sleep to our ability to learn, create memories, and solve problems. Sleep has also been tied to mood. Without enough sleep, a person has trouble focusing, and responding quickly — a potentially dangerous combination, such as when driving. In addition, mounting evidence links a chronic lack of sleep with an increased risk for developing obesity, diabetes, cardiovascular disease, and infections.

The quality of sleep is also important. How well rested you are and how well you function the next day depend on your total sleep time and how much of the various stages of sleep you get each night. Yet, each year an estimated 70 million adult Americans have some type of sleep problem.