What causes sleep apnea?

Sleep apnea can be caused by anatomical crowding of the airway, weakened throat muscles, excess weight, and impaired breathing control from the brain.

What actually causes sleep apnea and why it happens to some people but not others

Why does the airway collapse or breathing stop during sleep?

Sleep apnea arises from two main mechanisms: physical blockage of the throat (obstructive) and failed respiratory drive from the brain (central). Mixed apnea shows features of both.

Anatomical crowding narrows the pharynxA large tongue, enlarged tonsils, or a set-back lower jaw leaves less space for airflow. Up to 70 % of children with big tonsils show obstructive events.
Fat deposits around the neck add pressureIn adults, each 10 % gain in body weight can raise apnea–hypopnea index (AHI) by roughly 32 %. "Many people are surprised to learn that even modest weight gain can tip them into clinically significant apnea," says the team at Eureka Health.
Muscle tone falls sharply in REM sleepThroat muscles relax during deep sleep. If they are already weak—for example after alcohol intake—they cannot resist the negative pressure of inhalation and the airway snaps shut.
Brainstem signal failure causes central apneaHigh-altitude breathing, opioid medication, and heart failure can blunt the brain’s CO₂ response. Sina Hartung, MMSC-BMI, notes, "Central events often go unnoticed until someone sees Cheyne–Stokes breathing on a sleep study."}]},{
Which symptoms mean your sleep apnea is turning dangerous?
Back sleeping lets gravity pull the tongue backwardLying supine allows the tongue and soft palate to slump toward the throat; Stanford Health Care notes that this posture can block the airway even in people without enlarged tonsils. (StanfordHC)
Men and mid-life adults face higher collapse riskThe American Academy of Sleep Medicine reports that obstructive sleep apnea is more common in middle-aged adults and men, who often have larger neck circumferences and different fat distribution. (AASM)