NREM Stage N1 This stage of non-REM sleep is the typical transition from wakefulness to sleep and generally lasts only a few minutes. Stage N1 is the lightest stage of sleep; patients awakened from it usually don’t perceive that they were actually asleep During this stage: Eye movements are typically slow and rolling. heartbeat and breathing slow down muscles begin to relax you produce low amplitude mixed frequencies waves in the theta range (4 to 7 Hz) NREM Stage N2 This next stage of non-REM sleep comprises the largest percentage of total sleep time and is considered a lighter stage of sleep from which you can be awakened easily. This is the stage before you enter deep sleep. During this stage: heartbeat and breathing slow down further no eye movements body temperature drops Sleep spindles and K-complexes are two distinct brain wave features that appear for the first time NREM Stage N3 This final stage of non-REM sleep is the deepest sleep stage. Stage N3 sleep is known as slow-wave, or delta, sleep. Your body performs a variety of important health-promoting tasks in this final non-REM stage. During this stage: arousal from sleep is difficult heartbeat and breathing are at their slowest rate no eye movements body is fully relaxed delta brain waves are present tissue repair and growth, and cell regeneration occurs immune system strengthens REM Stage R There are two phases of REM sleep: phasic and tonic. Phasic REM sleep contains bursts of rapid eye movements, while tonic REM sleep does not. Stage R occurs about 90 minutes after you fall asleep, and is the primary “dreaming” stage of sleep. Stage R sleep lasts roughly 10 minutes the first time, increasing with each REM cycle. The final cycle of stage R may last roughly between 30 to 60 minutes. During this stage: eye movements become rapid during phasic REM breathing and heart rate increases and become more variable muscles become paralyzed, but twitches may occur brain activity is markedly increased When you fall asleep at night, you cycle through all of these stages of sleep multiple times — roughly every 90 minutes or so.