Statistical analysis
SECONDARY
Normality of continuous data was tested by Shapiro–Wilk test. Independent The intra-rater reliability for the upper airway variables was assessed using a two-way mixed, absolute agreement, single measures intraclass correlation coefficient (ICC). Reliability was defined as poor (ICC < 0.5), moderate (ICC = 0.5–0.75), good (ICC = 0.75–0.9), or excellent (ICC > 0.9) [Two-way analyses of variance (ANOVA) were used to compare the mean differences of all outcome variables separately for within-subjects factor (i.e., baseline without MAD versus follow-up with MAD in situ), for between-subjects factor (i.e., the mean of the outcome variables of MAD-H versus MAD-S), and to assess the interaction effect between the two factors (i.e., treatment effect between baseline and follow-up of MAD-H versus MAD-S) on the outcome variables. Any significantly different baseline characteristics between both MAD groups were controlled as covariates in the assessment of the interaction effect [A per-protocol (PP) analysis included patients who completed the entire treatment and was performed for all primary and secondary outcomes variables. An intention-to-treat (ITT) analysis included all patients who underwent randomization and was performed only for the primary outcome variables. In ITT analysis, the missing data were imputed by a multiple imputation procedure (five imputed datasets) in SPSS software (SPSS version 20, Chicago, IL, USA). A post hoc power analysis was conducted for the primary outcome variables using the software G*power (version 3.1.9, Franz Faul, Universität Kiel, Germany).