Changes in spectral variables at moderate altitude.

Variables are provided as change in percent of baseline. To take the order-effect of altitude exposure into account, the statistics were computed for the two groups LH (ascending from lower to higher altitude, n = 23) and HL (descending from higher to lower altitude, n = 21) separately. Data are provided as means (SEM). Post hoc t-tests were performed if factor Condition (pA; ns: not significant) of the mixed model ANOVA with factors Condition and Order of altitude exposure was significant.*pF3A2: Frontal derivation; C3A2: Central derivation; SWA: Slow-wave activity (0.8–4.6 Hz); Theta activity: Power in the 4.6–8 Hz range; Relative spindle peak height: Height of the spindle peak minus background activity at position of the peak; N1, N2: night 1 and 2 at higher altitude.