Figure 3.

Boxplots of three selected features (z-score values) including p-values of ANCOVA with education as a covariate. Sleep efficiency, slow wave power at O1 during N2 and sigma coherence at C3-C4 during REM were (prior to multiple comparison correction) significantly different between the groups. After Bonferroni–Holm correction, these tendencies were non-significant and should therefore not be considered as stand-alone features but combined in a multivariate approach. Cognition +, positive cognitive change; Cognition −, negative cognitive change