Healthy, quality sleep typically results in a continual night of sleep and the sense of feeling refreshed and alert when awoken. The duration of sleep is usually six to nine hours, with adults sleeping an average of 7.5 hours each day.
An adult’s 24-hour cycle is divided into 16 hours of wakefulness and eight hours of sleep. The on-going 24-hour circadian rhythms run parallel to the homeostasis process, also known as process “S”. The “S” process corresponds to sleep pressures that individuals accumulate during the wakefulness period before being able to fall asleep. With increasing sleep pressures, sleep is proportionately larger and deeper in the following recovery periods.
Sleep arousals are normal brief interruptions to sleep. While it is normal to experience some sleep arousals, when they become too frequent or long, healthy individuals may see detriment to their wakefulness in only a few days. Normally, it should take about ten to 15 minutes to fall asleep after going to bed. If you are asleep in less than five minutes, this could be a sign of excessive sleepiness.
Sleep arousals can be viewed as the body’s attempt to prepare the sleeping individual, in a low-vigilance state, to react to potential risk (a “fight or flight” state). Sleep apnea and hypopnea are respiratory distress-like events that trigger sleep arousal.
Sleep deprivation is most commonly characterized by a lack of sleep due to insufficient sleep duration. Sleep deprivation may also be caused by a lost sleep segment due to environmental factors, including noise. Both sleep deprivations and lengthy sleep durations have been associated with a higher risk of disease, even death.
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