Table 2 Correlations between PC scores of health indicators, obtained separately from NREM and REM data. Data is shown for all PCs that were retained based on Kaiser’s rule. High correlations indicate that the degree to which health indicators conformed to the stereotypical PSD change patterns revealed by the PCs was similar in NREM and REM, suggesting vigilance state-independent effects. Note that the sign of the correlation is unimportant as the sign of PC loadings is arbitrary and that the sign of REM loadings was flipped for visualization in Fig. 5 but not for the calculations shown in this table

From: Sleep alterations as a function of 88 health indicators