Sleep apnea: what obstructive sleep apnea is and why it interrupts breathing during sleep

What it actually is

Obstructive sleep apnea (OSA) is a breathing disorder marked by repeated episodes of partial (hypopnea) or complete (apnea) upper-airway obstruction during sleep, interrupting breathing for at least 10 seconds at a time. The American Academy of Sleep Medicine, in its International Classification of Sleep Disorders (ICSD-3, 2014), defines it and sets its reference measure: the apnea-hypopnea index (AHI), which counts these episodes per hour of sleep. Severity is classified by this index: mild (AHI 5–14), moderate (15–29), and severe (30 or more). A formal diagnosis requires, beyond an elevated AHI, associated symptoms such as excessive daytime sleepiness or a history of snoring with observed breathing pauses. It's the most common sleep-related breathing disorder in adults, though many cases go undiagnosed.

Why it happens during sleep

During sleep, the muscles that keep the upper airway open — including the tongue and soft palate — lose some of their usual tone, which is normal in everyone. In someone with sleep apnea, that relaxation is enough for the soft tissues of the throat to collapse partially or completely, blocking airflow. The effect intensifies during REM sleep, when generalized muscle atonia is deepest, which is why episodes tend to run longer and more often in that stage. Several factors raise the risk: excess weight (fat tissue around the neck narrows the airway), certain anatomical features (a recessed jaw, enlarged tonsils, a wide neck), and drinking alcohol or taking sedatives before bed, which relax the pharyngeal muscles further and prolong collapse episodes.

The real risks — and why snoring isn't the same as having apnea

Untreated sleep apnea has been consistently associated, in large epidemiological studies such as the Wisconsin Sleep Cohort (Peppard et al., 2000), with a higher risk of hypertension, and in later research, with elevated cardiovascular risk more broadly. It's worth stating this precisely: this is a documented statistical association, not an individual certainty — having sleep apnea doesn't mean you will necessarily develop these problems, and many additional factors play a role. Equally important: don't confuse snoring with apnea. Snoring is extremely common, and most people who snore don't have sleep apnea. What raises clinical suspicion isn't snoring on its own, but its combination with breathing pauses witnessed by someone else and episodes of gasping or choking on waking.

Signs it might be happening

Many signs of sleep apnea are noticed first by a bed partner or roommate rather than by the person themselves. The most characteristic are loud, habitual snoring, witnessed breathing pauses during sleep, and waking up gasping or choking. Daytime signs include excessive sleepiness — which can be assessed with a validated tool widely used in clinical practice, the Epworth Sleepiness Scale (Johns, 1991) — morning headaches, and morning dry mouth from breathing through an open mouth overnight. No single sign confirms the diagnosis on its own; it's the combination, especially a reported history of witnessed breathing pauses, that usually prompts a sleep evaluation.

What to do — and what not to expect from this article

This article is educational, not a diagnosis. The reference test for confirming sleep apnea is polysomnography, a sleep study (in a lab or, in selected cases, at home) that measures breathing, blood oxygen, and brain activity to calculate the AHI. If moderate or severe apnea is confirmed, the first-line treatment with the strongest clinical backing is continuous positive airway pressure (CPAP), a device that keeps the airway open during sleep with a steady flow of air. Its effectiveness depends on using it every night, and getting used to the mask is a real, well-documented hurdle for some people — talking to a specialist about different models and fitting usually solves it. In milder cases, or as a complementary measure, losing weight if overweight and cutting back on alcohol before bed are factors that can help reduce episodes. Ensuenia does not diagnose or treat sleep apnea; this page summarizes published scientific literature so you know what to ask, and who to ask.

The connection with bruxism

Sleep apnea doesn't just affect breathing — it's also been linked to other sleep phenomena, including bruxism. As we explain in our article on sleep bruxism, clenching or grinding episodes are typically preceded by nervous-system microarousals, and in people with obstructive apnea, the body's own effort to reopen the airway can trigger that microarousal and, with it, a bruxism episode. In other words: the sleep fragmentation caused by apnea can itself be a trigger for bruxism — which is why bruxism shows up more often in people with untreated obstructive apnea. If, on top of snoring or noticing breathing pauses, you've been told you grind your teeth at night, it may be worth mentioning both in the same consultation.

Frequently asked questions

Sources

• American Academy of Sleep Medicine, International Classification of Sleep Disorders, 3rd edition (ICSD-3) (2014) — Define la apnea obstructiva del sueño y establece el índice de apnea-hipopnea (IAH) y sus umbrales de gravedad.
• Murray W. Johns, A new method for measuring daytime sleepiness: the Epworth sleepiness scale (1991) — Sleep; presenta la Escala de Somnolencia de Epworth, herramienta validada de cribado de somnolencia diurna.
• Susheel P. Patil et al., Treatment of Adult Obstructive Sleep Apnea With Positive Airway Pressure: An American Academy of Sleep Medicine Clinical Practice Guideline (2019) — Journal of Clinical Sleep Medicine; guía de práctica clínica que respalda el CPAP como tratamiento de primera línea.
• Paul E. Peppard, Terry Young, Mari Palta, James Skatrud, Prospective Study of the Association Between Sleep-Disordered Breathing and Hypertension (2000) — New England Journal of Medicine; Wisconsin Sleep Cohort, base de la asociación epidemiológica entre apnea del sueño e hipertensión.