Sleep apnea is characterized by repeated interruptions in breathing while a person sleeps. These breathing pauses can occur hundreds of times each night, preventing restorative rest. Accurate diagnosis is obtained through a specialized overnight sleep study, known as polysomnography. This testing monitors various bodily functions during sleep to precisely measure the frequency and type of breathing disturbances, which determines the degree of the disorder.
Understanding Apnea and Hypopnea Events
A sleep study identifies two main types of respiratory events. An apnea is defined as a complete or near-complete cessation of airflow lasting ten seconds or longer, often causing a drop in blood oxygen saturation. A hypopnea is a partial but significant reduction in airflow, also lasting at least ten seconds, accompanied by either a drop in blood oxygen or a brief awakening.
Both events signify that the airway has collapsed or narrowed enough to disrupt normal breathing. The brain senses the lack of oxygen and triggers a momentary arousal to restart breathing, which the sleeper rarely remembers. The standard metric used to quantify the disorder’s severity is the Apnea-Hypopnea Index (AHI). The AHI is calculated by adding the total number of apneas and hypopneas recorded and dividing that sum by the total hours of sleep.
The Apnea-Hypopnea Index (AHI) Thresholds
For adults, an AHI score of less than five events per hour is considered normal. This level suggests minor breathing interruptions that do not meet the criteria for a sleep apnea diagnosis. Severity classification begins once the AHI reaches five or more events per hour.
A diagnosis of mild sleep apnea is given when the AHI falls between 5 and 14 events per hour. Moderate sleep apnea is indicated by an AHI score ranging from 15 to 29 events per hour. A severe diagnosis applies to any adult with an AHI of 30 or more events per hour, meaning breathing is interrupted at least once every two minutes. These boundaries standardize diagnosis and guide treatment decisions.
Connecting AHI Scores to Health Risks
The severity level indicated by the AHI score is directly related to health consequences. With each event, the body is briefly stressed by a lack of oxygen and a sudden spike in blood pressure. Higher AHI scores mean these stressful events occur more frequently, placing a chronic strain on the cardiovascular system.
Untreated sleep apnea, especially in the moderate to severe ranges, significantly raises the risk of developing hypertension, or high blood pressure. This consistent nocturnal stress contributes to a higher likelihood of cardiovascular issues and metabolic problems. The sleep fragmentation caused by these events also leads to excessive daytime sleepiness and reduced concentration.
Associated Health Risks
- Heart attack
- Stroke
- Irregular heart rhythms
- Type 2 diabetes
- Increased risk of accidents while driving or operating machinery
Next Steps After Diagnosis
Once a sleep apnea diagnosis is confirmed, a healthcare provider recommends a management plan based on the AHI score. For moderate to severe cases, Continuous Positive Airway Pressure (CPAP) therapy is the most common and effective option. This treatment involves wearing a mask that delivers pressurized air to keep the airway open during sleep.
For individuals with mild or moderate sleep apnea, other options may be explored, sometimes alongside CPAP. Custom-fitted oral appliances reposition the jaw and tongue to prevent airway collapse and can be a suitable alternative. Lifestyle adjustments, such as weight loss and avoiding sleeping on the back, are also recommended as they can decrease the frequency of breathing events.