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Common Sleep Disorders
Sleep is defined as a natural and periodic state during which consciousness of the world is suspended. Contrary to popular belief, sleep is not simply a state in which the brain is resting, but a dynamic, complex condition during which the brain is very active.
There are four distinctive stages of sleep - N1, N2, N3 and REM or rapid eye movement. Stages N1, N2, and N3 are considered non-REM. Certain stages of sleep may be important not only for maintaining alertness, but also for hormonal secretion, immune function, learning and memory.
Throughout an eight-hour sleep cycle, the brain cycles through the different sleep stages from N1 to REM and then back to N1. Each stage of sleep is defined by specific brain and muscle activity, eye movements, breathing, and sometimes other signs such as oxygen in the blood, leg movements and heart rate.
Non-REM and REM sleep alternate in 90- to 110-minute cycles. A normal sleep pattern has 4-5 cycles.
Non-REM Sleep
Non-REM sleep consists of the first three stages of sleep that range from light dozing to deep sleep. Throughout this state of sleep, muscle activity is still functional, breathing is low, and brain activity is minimal. Approximately 75% of the sleep cycle is spent in non-REM sleep.
REM sleep
REM is very different from the other stages of sleep because brain waves actually look more like the active patterns seen when the person is awake. Periodic eyelid fluttering, muscle paralysis, and irregular breathing, with variations in body temperature, heart rate, and blood pressure distinguish REM from non-REM sleep. Most dreaming occurs during REM sleep. Although brief images can occur during other stages, the detailed experiences most people associate as dreams occur during this stage. During REM sleep the brain actually blocks signals to the muscles to keep them immobile, so dreams cannot be acted out.
Adults spend about 20 - 25% of their sleep cycle in REM sleep. Many researchers believe that REM sleep in particular is required for building certain types of memories.
When you have difficulty sleeping or don't get enough sleep to get through a day, it could be a sign you're suffering from a sleep disorder. It's important to talk to your doctor or a sleep specialist as these can be diagnosed and are treatable.
Do you have a sleep disorder? Take our sleep assessment test.