Better Sleep Articles >> Understanding SleepThe Stages of SleepPOSTED: July 29, 2007 2:05 pm  Stage 1:
Light sleep. We drift in and out and can be awakened easily. Our eyes move slowly and muscle activity slows.
Stage 2:
Our eye movements stop and our brain waves become slower with occasional bursts of rapid waves called sleep spindles.
Stage 3:
Deep sleep. Extremely slow brain waves called delta waves appear, interspersed with smaller, faster waves.
Stage 4:
Deep sleep. The brain produces mostly delta waves. There are no eye movements and no muscle activity.
Stage 5:
REM sleep. Breathing becomes more rapid, irregular, and shallow. Eyes jerk rapidly, limb muscles become temporarily paralyzed. Dreams almost always happen in this stage, but may occur in other sleep stages as well.
We usually pass through five stages of sleep. Each cycle takes about two hours. Then the cycle starts over again with stage 1. As the cycles repeat, deep sleep periods get shorter and periods of REM sleep lengthen. Adults spend half of their sleep time in stage 2, 20 percent of the time in REM sleep, and 30 percent in the other stages. Infants start out spending about half of their sleep time in REM sleep.
(Source: National Institutes of Health) |
