Both the Duration of Apnea and the Number of Apneas Are Important in Obstructive Sleep Apnea Syndrome

Abstract

Apnea and hypopnea are generally considered to be equivalent in calculating the apnea-hypopnea index (AHI) regardless of their kind and duration. However, we supposed that apnea and hypopnea could differ in their effects on arousal and oxygen desaturation, and that the duration of an occurrence of apnea or hypopnea could also be important. The following were analyzed for 182 casesof polysomnography in obstructive sleep apnea (OSA) patients. 1) We calculated the correlations between variables, such as AHI, arousal index, oxygen desaturation index (ODI), apnea index (AI),hypopnea index (HI), and mean apnea duration, using common statistical procedures. 2) We compared AHI, arousal index, and ODI in patients divided into short and long mean apnea-duration groups. We found that 1) AHI, arousal index, ODI, mean apnea duration, and AI were highly correlated with each other, but HI was not; and 2) arousal index and ODI were higher in the long mean apnea-duration group than in the short mean apnea-duration group. Hence apnea is more important for arousal and oxygen desaturation during sleep than is hypopnea. Longer apnea duration is associated with both more severe OSA and greater arousal and oxygen desaturation.