Snoring is the sound that is made by the vibration of breathed-in air passing through narrowed airway passages during sleep, producing nasal or guttural sounds. It may be simple or complicated by obstructive sleep apnea. It may be associated with disturbances of one’s own sleep or that of others sharing the room. It may be loud or soft, persistent or temporary.
A grading system has been developed to help quantify how severe snoring is. It includes three grades of snoring, namely:
- Grade 1: This is also termed simple snoring. The individual snores once in a while, and not very loudly. Breathing remains normal and health problems associated with this snoring are minimal. The only negative outcome may be if the sleep partner is a light sleeper or is disturbed by the snores. This may cause personal disagreements between the partners, in which case treatment may be sought.
- Grade 2: individuals with grade 2 snoring exhibit snoring behavior on three or more days of every week. They may have some difficulty with breathing, from mild to moderate, during sleep. This sleep-associated breathing problem may result in daytime sleepiness and fatigue.
- Grade 3: In this type of snoring, the sleeper snores very loudly, so that the sound is heard outside the bedroom. In many cases the individual suffers from obstructive sleep apnea (OSA). As a result, the airways are totally or partially obstructed for ten seconds on average. This causes the brain to shift from deep sleep to lighter stages prematurely, depriving the person of sufficient restful sleep. Many people with OSA wake up during this phase for a brief time, though they have no memory of the wakenings. Several such episodes occur during the night, which translates to acute sleepiness the next day and often falling asleep during normal conversation or work. This, of course, impairs performance and social functioning.
Power spectrum and snoring
The use of the power spectrum aims to record the snore intensity and frequency at the same time. Simple snores usually peak at 100-300 Hz, in contrast to the OSA snore which typically peaks above 1000 Hz. Using the energy-power-time equation, snore maps have been created which classify snores as follows:
- Type 1: low-frequency, single syllable snore
- Type 2: low and middle frequency duplex sound
- Type 3: high and middle frequency duplex sound
- Type 4: triplex sounds with high, low, and middle frequency
These may be used to assess the severity of OSA more accurately than using subjective questionnaires. High-frequency snore signals indicate greater OSA, or obstruction of the upper airway by the tongue base or tonsil. Low-frequency sounds are typical of soft palatal obstruction. Mid-frequency sounds indicate epiglottic snores.
Again, studies have shown two patterns of snoring with regards to waveforms of the generated sound. Brief airway closure causes complex waveforms to appear, but vibration of an airway which remains open causes simple waveforms. These are often combined to form complex patterns in OSA, and these remain difficult to interpret.
Reviewed by Afsaneh Khetrapal BSc (Hons)