Quick Overview
- What does the Apnea-Hypopnea Index do: It measures the average number of apnea and hypopnea events per hour of sleep, classifying OSA severity as mild (5–15), moderate (15–30), or severe (>30).
- AHI is widely used but has limitations. That is due to the fact that it doesn’t account for the duration of events or differences in event types. For example, longer or more frequent apneas may have more serious effects than shorter ones.
Apnea-hypopnea Index (AHI)
The apnea-hypopnea index (AHI), is the combined average number of apneas and hypopneas that occur per hour of sleep. According to the American Academy of Sleep Medicine (AASM), it is categorized into mild (5-15 events/hour), moderate (15-30 events/hr), and severe (>30 events/hr).
AHI has been utilized in the majority of research, to assess the severity of obstructive sleep apnea (OSA) and the effectiveness of treatment. In both clinical practice and research, it does not appear to be a suitable method for assessing the severity of the condition or for choosing a course of treatment.
As an example, in a study evaluating two patients with the same AHI (like 60), the severity of the disease is assumed to be the same in both patients. Nevertheless, the mean time of apnea- hypopnea, might be longer in one patient than the other (12sec vs 50sec). In this scenario, the objective is to determine whether both patients are suffering from the same severity, or the longer apnea-hypopnea causes more severe conditions.
While hypopnea may be more common in one patient, apnea may be the main respiratory episode in another. Since apnea is a complete halt, it should be remembered that it can cause a greater decrease in airflow and arterial oxygen saturation than hypopnea.
Numerous investigations, have demonstrated that the illness complications and thus the treatment response, may not be quantified by AHI. Although, they appear to be a disease burden, mood disorders are unrelated to the degree of OSA as determined by the AHI. Furthermore, AHI is not linked to OSA-related quality of life, despite the fact that individuals with OSA experience a major deterioration in this area.
In light of the aforementioned issues, the majority of disagreements in the field of sleep apnea have arisen, because the AHI is unable to accurately assess the severity of the condition. A new index should be created, to measure the severity of the condition more accurately than AHI, in order to effectively assess sleep apnea. Along with the average number of occurrences per hour, the apnea/hypopnea ratio and the average duration of apnea and hypopnea events, should be taken into account while calculating this index. This indicator, could be useful to doctors as they determine the best course of treatment or evaluate the prognosis.
