Severity of obstructive sleep apnea (OSA) is estimated based on respiratory events per hour [i.e., apnea-hypopnea index (AHI)]. The aim of this study was to investigate effects of weight change on the severity of respiratory events. Respiratory event severity, including duration and morphology, was estimated by determining parameters quantifying obstruction and desaturation event lengths and areas, respectively. Respiratory events of 54 OSA patients treated with dietary intervention were evaluated at baseline and after 5-year follow-up in subgroups with different levels of weight change. AHI, oxygen desaturation index (ODI) and obstruction event severities decreased during weight loss. In lower level weight loss, the decrease was milder in obstruction severity than in AHI and ODI, indicating that the decrease in the number of events is more focused on less severe events. In weight gain groups, parameters incorporating obstruction event severity, AHI and ODI increased, although increase was greater in parameters incorporating obstruction event severity. The number and severity of respiratory events were modulated differently by the level of weight change. AHI misses this change in the severity of respiratory events. Therefore, parameters incorporating information on the respiratory event severities may bring additional information on the health effects obtained with dietary treatment of OSA.
Keywords: Nocturnal respiratory events; Novel parameters; Obstruction severity; Sleep apnea; Weight gain; Weight loss.