Prevalence of sleep apnea in multiple sclerosis patients meeting clinical eligibility criteria for the Sleep Apnea in Multiple Sclerosis Positive Airway Pressure (SAMSPAP) trial

Background: We have previously described a relationship between severe fatigue and obstructive sleep apnea (OSA) in MS patients (Mult. Scler. J. Vol 18; 1159‐1169). SAMSPAP (NCT01746342) is a randomized, controlled trial evaluating the effects of PAP treatment of OSA on fatigue in MS patients. The objective of the present analysis was to assess the prevalence of OSA among MS patients meeting the clinical eligibility criteria for this study. Methods: Patients with confirmed MS on stable immunomodulating medication were recruited from the MS clinics at our institutions. Clinical eligibility criteria included: Expanded Disability Status Scale score (EDSS) ≤7, severe fatigue (Fatigue Severity Scale (FSS) score ≥ 4), poor subjective sleep quality (Pittsburgh Sleep Quality Index (PSQI) >5) and no more than minimal cognitive impairment (Montreal Cognitive Assessment (MoCA) ≥26). OSA was defined by an Apnea‐Hypopnea Index (AHI) ≥ 15 events/h on complete overnight polysomnography (PSG) scored using American academy of sleep medicine research (Chicago) criteria. Results: 87 subjects (35% male) were evaluated in an initial screening visit. Of these, 74 (83%) met the clinical eligibility criteria and underwent PSG. Reasons for exclusion included (n); withdrawal before completing screening (4); low FSS (5); low MoCA (5); and low PSQI (1). Subjects undergoing PSG had mean(±SD) age=49±9 y, BMI=28±6 kg/m2, EDSS=4±2, MoCA=28±1, FSS=6±1 and PSQI=11±4, and on PSG had total sleep time=5.5±1.1h, AHI=30±22/h, 4% Oxygen Desaturation Index (ODI) =5±8/h and Central apnea index = 1±2/h. 54 of 74 subjects had OSA (mean AHI = 37±21/h, ODI 6.4 ± 8.5, respiratory arousal index =34±20/h), of whom 9 surpassed our pre‐specified OSA safety threshold for randomization to this 6‐month, sham PAP‐controlled trial (AHI > 30 with either 4% ODI>15/h (n=8) or Epworth Sleepiness score ≥ 15 (n=1)). The positive predictive value for OSA of our clinical eligibility criteria was 73% (95% CI 61‐83%), and for severe OSA (AHI >30/h) was 40% (95%CI 29‐53%). Conclusion: These findings suggest that a diagnosis of OSA should be considered among ambulatory MS patients pesenting with severe fatigue and poor subjective sleep quality. The results of the ongoing SAMSPAP trial will provide new insights ito the impact of OSA treatment on severe fatigue in MS patients.