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Sleep-onset SWS (SOSWS) is a short [[wikipedia:Slow-wave_sleep|slow-wave-sleep]] latency, or an abnormally rapid transition from wakefulness to SWS, almost fully skipping the period of [[wikipedia:Non-rapid_eye_movement_sleep|light sleep]] that normally characterizes the beginning of the sleep period.

'''Sleep-onset SWS''', or '''SOSWS''', is a phenomenon in which [[wikipedia:Slow-wave_sleep|slow-wave-sleep]] onset latency is greatly reduced, wherein an individual transitions rapidly from wakefulness to SWS, shortening the period of [[wikipedia:Non-rapid_eye_movement_sleep|light sleep]] that normally characterizes the beginning of the sleep cycle.

== Mechanism ==

== Mechanism ==

After periods of [[wikipedia:Sleep_deprivation|sleep deprivation]], and slow-wave-sleep deprivation in particular, a significant shortening of [[Scheduling overview#Sleep stages|NREM3]] and NREM4 latencies is usually expected.<ref name="swsd" /> Similarly to [[SOREM|sleep onset REM]]<ref name="aasm" />, SWS latency is <15 minutes in this case.

After a sustained period of [[wikipedia:Sleep_deprivation|sleep deprivation]], especially of SWS, SWS becomes prioritised by the body and its onset latency greatly reduces.<ref name="swsd" /> Similarly to [[SOREM|sleep-onset REM]]<ref name="aasm" />, SWS latency can reduce to less than 10 to 15 minutes.

== Application to polyphasic sleep ==

== Application to polyphasic sleep ==

Generally polyphasic sleep schedules, which contain at least 3 full [[wikipedia:Sleep_cycle|sleep cycles]] in [[Cores|core(-s)]], rarely cause significant SWS loss. SOSWS is more common for extreme schedules, such as the [[Nap only|nap-only]] line. This mechanism causes entering SWS almost immediately, which allows to get SWS-filled [[naps]].

Most polyphasic sleep schedules, which contain at least 3 full [[wikipedia:Sleep_cycle|sleep cycles]] in [[Core|core(s)]], rarely cause significant SWS loss. SOSWS is more common for extreme schedules, such as the [[Nap only|nap-only]] schedule line. This mechanism causes entering SWS almost immediately, which produces SWS-filled [[Nap|naps]] on these schedules. Under such circumstances, these naps can become extremely difficult to wake up from, even more so then REM-filled naps after [[REM rebound]]. This represents one of the main obstacles in [[Uberman#Adaptation|adapting to a nap-only schedule]].

== References ==

== References ==