Apnea-hypopnea index (AHI)

Definition:

The apnea-hypopnea index is the combined average number of apneas and hypopneas that occur per hour of sleep.

An apnea is when breathing completely stops for a period of time during sleep, and a hypopnea is when breathing becomes shallow for ten seconds or more.

In this way, the apnea-hypopnea is a rough measure of the severity of sleep apnea – a condition commonly associated with excess weight that interferes with sleep quality.