Statistical analysis

All the data were analyzed using SPSS software (version 19.0; IBM SPSS, Armonk, NY, USA) and MedCalc (version 12.7.3; MedCalc Software bvba, Ostend, Belgium). Values are presented as the mean ± standard deviation for continuous variables, and as a number or percentage for categorical variables, as appropriate. The correlation between AHI_PSG and AHI_MSM was evaluated using Pearson's correlation coefficient. One-sample t-test was used to evaluate the difference between AHI_PSG and AHI_MSM. Bland-Altman analysis was performed using MedCalc to assess the similarity between AHI_PSG and AHI_MSM. OSA was diagnosed in patients that have a higher AHI than the cut-off value. Thus, cut-off points of AHI_PSG were estimated to increase the precision of the AHI_MSM device using the area under the receiver operating characteristic (ROC) curves. To assess the predictive performance of the MSM, sensitivity and specificity were also calculated. P<0.05 was considered to indicate a statistically significant difference.