What causes low oxygen levels while sleeping?

As a pulmonologist with extensive experience in sleep medicine, I can explain the factors that contribute to low oxygen levels during sleep. There are several medical conditions and physiological changes that can lead to this phenomenon: 1. Central Sleep Apnea (CSA): This is a disorder where the brain fails to send the correct signals to the muscles that control breathing during sleep, leading to brief periods where breathing stops or becomes very shallow. 2. Obstructive Sleep Apnea (OSA): A more common condition where the airway is physically blocked or collapses during sleep, causing interruptions in breathing. 3. Cheyne-Stokes Respiration: This is a pattern of breathing characterized by gradual increases and decreases in the depth of breathing, often seen in people with heart failure or in the later stages of neurological disorders. 4. High-altitude Acclimatization: At higher altitudes, the air pressure is lower, which means there is less oxygen available in the air. This can lead to lower oxygen saturation levels during sleep. 5. Pulmonary Diseases: Conditions like chronic obstructive pulmonary disease (COPD), interstitial lung disease, and pneumonia can impair the lungs' ability to oxygenate the blood. 6. Anemia: A reduced number of red blood cells or hemoglobin can decrease the blood's capacity to carry oxygen. 7. Medications: Certain medications can suppress the respiratory drive and lead to lower oxygen levels during sleep. 8. Positional Sleep: Sleeping in certain positions, especially on the back, can sometimes cause or exacerbate breathing problems. 9. Age: As people age, their respiratory system may not function as efficiently, leading to lower oxygen levels during sleep. It's important to note that while everyone's oxygen levels naturally decrease during sleep, significant drops in oxygen saturation (below 90%) can be a sign of a serious sleep disorder and should be evaluated by a healthcare professional. If your waking oxygen saturation is greater than about 94 percent on room air, it is unlikely that your saturation during sleep will fall below 88 percent, which is considered the lower limit of normal.

Everyone's oxygen levels in the blood are lower during sleep, due to a mildly reduced level of breathing. Also, some alveoli drop out of use during sleep. If your waking oxygen saturation is greater than about 94 percent on room air, it is unlikely that your saturation during sleep will fall below 88 percent.