Statistical analyses
PPG values are presented as the mean \(\pm\) standard error of mean (SEM). The criterion of statistical significance was \(p<0.05\) for all PPG characteristics. We applied Origin (OriginLab Corp.) for the ROC-analysis and for the two-way ANOVA at the \(\alpha\)=0.05 to test for differences between PPG amplitudes and the age and sex of study subjects. Statistical characteristics including correlation coefficient, sensitivity, specificity, positive and negative predictive value (PPV and NPV, respectively), and accuracy were calculated using MATLAB.
RESULTS