Snoring and sleep terms, in plain English.
Twelve terms that come up again and again. Each in two or three sentences.
- AHI (apnoea-hypopnoea index)
- How many times an hour breathing stops (apnoea) or becomes shallow (hypopnoea) during sleep. Under 5 is normal; 5 to 15 mild, 15 to 30 moderate, over 30 severe. It measures breathing, not snoring.
- OSA / OSAHS (obstructive sleep apnoea)
- A condition where the airway repeatedly collapses during sleep, interrupting breathing. Most people with it snore, but most people who snore don’t have it. NICE uses the longer name OSAHS.
- Primary (simple) snoring
- Snoring without breathing interruptions or daytime sleepiness. It’s a noise problem rather than a medical one, though it can only be called “simple” after breathing has been checked.
- Mandibular advancement device (MAD, splint, oral appliance)
- A mouthpiece that holds the lower jaw slightly forward during sleep to keep the airway open. Dentist-made or mouldable at home. The adult guidelines’ main non-CPAP option.
- Tongue-retaining device (TRD)
- A mouthpiece that holds the tongue forward by suction instead of moving the jaw.
- UPPP (uvulopalatopharyngoplasty)
- Surgery that removes or tightens soft tissue at the back of the throat, often with the tonsils.
- Polysomnography (sleep study)
- An overnight recording in a sleep clinic: breathing, oxygen, heart rate, brain activity and body position. The reference test for sleep apnoea.
- Home sleep test
- A simpler overnight recording done in your own bed with a small device. Enough to diagnose many cases; less complete than a clinic study.
- CPAP / APAP
- Continuous positive airway pressure: a machine that keeps the airway open with air pressure through a mask. APAP adjusts the pressure automatically. Treatment for sleep apnoea, not for snoring alone.
- Epworth Sleepiness Scale (ESS)
- An eight-question score of how likely you are to doze off in everyday situations. Over 10 suggests excessive daytime sleepiness and is one reason a doctor orders a sleep study.
- RDI (respiratory disturbance index)
- Like the AHI, but also counts partial breathing disturbances that wake you briefly without lowering oxygen. Often a little higher than the AHI for the same night.
- Nasal valve
- The narrowest part of the nasal passage, just inside the nostril. If it collapses when you breathe in, nasal strips and internal dilators are the devices designed for that specific problem.
Original sources & their limits
- Clinical practice guideline: oral appliance therapy for snoring and sleep apnoea (AASM & AADSM, 2015) ↗
Read in full. Recommends oral appliances for adults with primary snoring who want treatment, after a sleep physician has assessed them. Prefers custom, adjustable devices for people with sleep apnoea (based on low-quality evidence).
- NICE guideline NG202: obstructive sleep apnoea/hypopnoea syndrome in over-16s (2021) ↗
Read from a hosted copy of the guideline PDF (the NICE site refused our fetch). Offers CPAP for moderate or severe OSAHS; for mild OSAHS only when symptoms affect daily life; mandibular advancement splints when CPAP is not tolerated; positional modifiers for mild/moderate positional OSAHS. It does not cover simple snoring.
- Treatment of adult OSA with positive airway pressure: AASM clinical practice guideline (2019), summary ↗
AASM one-page summary read. Full guideline: Patil et al., J Clin Sleep Med 2019;15(2):335-343. PAP is recommended for adults with OSA and sleepiness (strong); CPAP and auto-PAP are treated as interchangeable for ongoing use.
Sources checked 26 Oct 2026.