What Are Sleep Disorders?Sleep can be divided into two types: REM sleep and non-REM (NREM) sleep. NREM sleep has four stages of increasingly deep sleep. Stage 1 sleep is the lightest, while stage 4 is the deepest.During normal sleep, you cycle through these types and stages of sleep. But if your sleep is repeatedly interrupted and you cannot cycle normally through REM and NREM sleep, you may feel tired, fatigued, and have trouble concentrating and paying attention while awake. Sleepiness puts you at greater risk for car wrecks and other accidents.Recommended Related to Sleep DisordersToo Sleepy for Sex?Too tired for *? Join the club. Up to 50% of U.S. adults skip or avoid * because they're too tired, recent polls show. It?s no wonder. The workday can extend long into the night, many couples have children and pets to tend to, and everyone has diversions that tempt their attention away from their partners -- and from sleep. "We?re a 24/7 society. We're burning the candle at both ends -- most of us -- so we are tired," says William Kohler, MD, director of Florida Sleep Medicine outside...Read the Too Sleepy for Sex? article > >If you have trouble getting to sleep or sleeping through the night, if you wake up too early or have a hard time waking up at all, or if you are overly tired during the day, you may have one of the following sleep problems.Circadian Rhythm DisordersTypically, people sleep at night -- thanks not only to the conventions of the 9-to-5 workday, but also to the close interaction between our natural sleep and alertness rhythms, which are driven by an internal "clock."This clock is a small part of the brain called the suprachiasmatic nucleus of the hypothalamus. It sits just above the nerves leaving the back of our eyes. Light and exercise "reset" the clock and can move it forward or backward. Abnormalities related to this clock are called circadian rhythm disorders ("circa" means "about," and "dies" means "day").
