Facts about the Sleep Cycle
- 08
Heart rate drops by 10 to 20 beats per minute during non-REM sleep stages, reaching its lowest point during deep sleep when metabolic demands are reduced.
- 07
Approximately 25 percent of your total sleep time is spent in REM sleep, where vivid dreams occur and your brain consumes as much energy as during waking hours.
- 06
Cortisol levels drop to their lowest point around midnight during sleep, then gradually rise throughout the night to peak upon waking around 6 to 8 AM.
- 05
Slow-wave sleep, comprising stages three and four of the sleep cycle, accounts for approximately 15 to 20 percent of total sleep time in adults but can comprise up to 50 percent in infants.
- 04
Melatonin production in the pineal gland peaks around 2 to 3 AM in humans, creating the deepest sleep window of the night cycle.
- 03
Brain temperature rises by approximately 0.5 degrees Celsius during deep sleep stages, peaking around the third and fourth stages of the sleep cycle.
- 02
Each complete sleep cycle lasts approximately 90 minutes and progresses through four distinct stages before repeating 4 to 6 times throughout a typical 8-hour night.
- 01
During REM sleep, your eyes move rapidly side to side approximately 60 to 100 times per minute while most voluntary muscles remain paralyzed.