Schedule an appointment today:

Book an Appointment

Sleep Medicine Acronyms (From APAP to Zzzz): Part 4, S-Z

Here is a series on abbreviations you are likely to encounter during your visits to a sleep specialist or sleep center.

This fourth section highlights terms that start with the letters S through Z.

See also:

  • Sleep Medicine Acronyms (From APAP to Zzzz): Part 1, A-D
  • Sleep Medicine Acronyms (From APAP to Zzzz): Part 2, E-M
  • Sleep Medicine Acronyms (From APAP to Zzzz): Part 3, N-R

Sleep Medicine Acronyms (S-Z)



Sleep Breathing Disorder/Sleep Related Breathing Disorder/SleepDisordered Breathing . This term referencessleep disorders which impair respiratory system processes during sleep. They include snoring, upper airway resistance, sleep apnea, and hypoventilation. Learn more:


Sleep Latency . This measures the length of time that it takes to fall sleep, usually in stage 1 nonREM sleep, though sleep may also be initiated in other sleep stages. It is SL that is critically examined during the sleep test known as the MSLT.


Sleep Onset . This is the moment you fall asleep, usually in stage 1 nonREM sleep.


Sleep Onset REM Period . A REM period that occurs at sleep onset. This is atypical, as most people transition from wakefulness to stage 1 nonREM sleep. The presence of SOREMPs during an MSLT or “nap test” indicates the potential for a diagnosis of narcolepsy.Learn more:


Blood Oxygen Saturation . This is expressed as a chemical equation:The S stands for saturation , the P stands for pulse , and the O2 stands for oxygen . A fingertip sensor known as a pulse oximeter is used during a sleep study to measure trends in both blood oxygen saturation and pulse throughout the test.


Slow Wave Sleep . This is another name for stage 3 nonREM sleep, delta sleep, or deep sleep. Brain waves during slow wave sleep show a distinctive delta wave pattern. It is during this stage of sleep that the brain releases growth hormone into the bloodstream to help heal the body at the cellular level.



Upper Airway Resistance Syndrome. A form of sleep-breathing disorder in which there are increases in resistance to airflow in the upper airway during sleep; this leads to brief arousals and daytime fatigue, even in the absence of apneas.Learn more:



Wake After Sleep Onset. The total amount of time spent awake after sleep has been initiated. WASO is a marker of sleep fragmentation , in which people fall asleep, then awaken frequently all night during and between each sleep cycle. A high WASO index on a sleep study may reveal the cause of someone’s excessive daytime sleepiness or confirm the presence of other sleep disorders.

Further Reading

News & Updates

Telehealth Patient

Telehealth for sleep evaluations

Telehealth is a hot topic. Although its recent rise is partially linked with the decline in in-person visits during the coronavirus pandemic, telehealth has in fact been heralded as the ‘next big thing’ in healthcare for more than a decade. The American Academy of Sleep Medicine (AASM) has announced its commitment to advancing the use…

Read more
sleep apnea and insomnia patient

Will Sleep Apnea Cause Insomnia?

Everyone has trouble sleeping at some point in their life. A late-afternoon latte, an overly indulgent dinner or nerves about an upcoming work milestone can keep you up into the wee hours of the night. The next day may not be one of your best –- you might be irritable, exhausted and unfocused — but…

Read more

Sleep Apnea Raises Your Risk of Sudden Cardiac Death: Get the Facts

You may have heard of sleep apnea, but do you really know what it is? Far from a harmless sleep disorder that keeps you from a sound night’s rest, sleep apnea can lead to serious health complications, including sudden cardiac death. According to the American Sleep Apnea Association, 22 million Americans suffer from sleep apnea.…

Read more