Novel parameters reflect changes in morphology of respiratory events during weight loss.

Apnea-hypopnea-index (AHI), disregarding the respiratory event morphology, is currently used in estimation of severity of obstructive sleep apnea (OSA). The purpose of the current study was to evaluate the potential of novel parameters in estimation of changes in severity of OSA during weight loss. Polygraphic data of 67 patients, 37 in the control (no weight loss) and 30 in the weight loss (>5%) groups was evaluated at baseline and after two year follow-up. Changes in the values of novel parameters, incorporating detailed information of respiratory event characteristics, were evaluated and compared with changes in AHI. The median AHI in the weight loss group decreased significantly during the follow-up. The number of shorter respiratory events decreased in the weight loss group, while the longer ones remained, increasing the median durations of the respiratory events by 20-62%. For this reason the decrease of the values of the novel parameters were smaller compared to AHI in the weight loss group. This suggests that the severity of OSA might not fall as linearly during weight loss as AHI suggests. Moreover, the novel parameters containing more detailed information on the morphology characteristics may provide valuable supplementary information for the assessment of the severity of OSA.