P019 Obstructive sleep apnoea endotypes in people with multiple sclerosis

PURPOSE: Obstructive sleep apnoea (OSA) is common in people with multiple sclerosis (MS) despite a lack of typical risk factors for OSA in people with MS such as obesity and male predominance. Therefore, underlying factors other than sex and obesity may be particularly important in the pathogenesis of OSA in people with MS. Thus, the primary aim of this study was to determine the relative contributions of OSA endotypes in people with MS and compare this to matched controls with OSA only. METHODS: Eleven people with MS and OSA (MS-OSA group) (apnoea-hypopnoea index [AHI]>5events/h) and eleven controls matched for OSA severity, age and sex without MS (OSA group) were studied. Participants underwent a detailed overnight polysomnography with an epiglottic pressure catheter and genioglossus intramuscular electrodes to allow for quantification of pathophysiological contributors to OSA. This included the respiratory arousal threshold, genioglossus muscle responsiveness, respiratory loop gain and upper airway collapsibility. RESULTS: Measures of the four primary OSA endotypes were not different between the MS-OSA and OSA groups (e.g. NREM respiratory arousal threshold -27±15 vs. -23±8 cmH(2)O respectively, p=0.24). Within group analysis indicated higher loop gain in non-obese MS-OSA participants compared to obese MS-OSA participants (0.53±0.11 vs. 0.37±0.11, p=0.04). CONCLUSIONS: Overall, OSA endotypes are similar between MS-OSA participants and matched OSA controls. However, within the MS-OSA group, non-obese participants have higher loop gain (unstable respiratory control) compared to obese participants. Thus, unstable respiratory control may play an important role in OSA pathogenesis in many people with MS.