When you're awake, throat muscles help keep your airway stiff and open so air can flow into your lungs. When you sleep, these muscles are more relaxed. Normally, the relaxed throat muscles don't stop your airway from staying open to allow air into your lungs.
But if you have obstructive sleep apnea, your airways can be blocked or narrowed during sleep because:
Not enough air flows into your lungs when your airways are fully or partly blocked during sleep. This can cause loud snoring and a drop in your blood oxygen levels.
When the oxygen drops to dangerous levels, it triggers your brain to disturb your sleep. This helps tighten the upper airway muscles and open your windpipe. Normal breaths then start again, often with a loud snort or choking sound.
The frequent drops in oxygen levels and reduced sleep quality trigger the release of stress hormones. These compounds raise your heart rate and increase your risk for high blood pressure, heart attack, stroke, and irregular heartbeats. The hormones also raise the risk for or worsen heart failure.
Untreated sleep apnea also can lead to changes in how your body uses energy. These changes increase your risk for obesity and diabetes.