Table 1.
Sleep cycle analysis.
Figure 1.
Relative non-REM sleep EEG power density spectra at moderate altitude.
Upper panels: Spectra at altitude (1630 m and 2590 m, N1 [first night] and N2 [second night]) are plotted relative to baseline sleep (490 m; line at 1). Significant differences (p<0.05, post-hoc paired t-test) between baseline and altitude are indicated by “+” (n = 44). Frequency resolution: 0.2 Hz. Lower panels: F-values of the frequency bins with significant p-values for factor Condition (490 m N1, 1630 m N1, 1630 m N2, 2590 m N1 and 2590 m N2) of mixed model ANOVA with factors Condition and Order. F3A2: frontal derivation; C3A2: central derivation. Due to technical problems during N2 at 2590 m, the EEG data of two subjects were incomplete and these two nights were excluded from the analysis.
Figure 2.
Relative slow-wave and theta activity at moderate altitude.
Mean (SEM; n = 44) slow-wave (SWA; 0.8–4.6 Hz) and theta activity (4.6–8 Hz) in non-REM and REM sleep (REMS) at altitude (1630 m and 2590 m, N1 [first night] and N2 [second night] at a particular altitude) expressed as percentage of baseline sleep at 490 m (100%; dotted line). F3A2: Frontal derivation; C3A2: Central derivation. *p<0.05 (paired t-test altitude compared to baseline).
Figure 3.
Sleep spindle characteristics.
Spindle peak frequency: Average frequency of spindle peak in non-REM sleep EEG spectra. Relative spindle peak height: Peak height minus background activity at location of the peak. Data were derived from visually identified spindle peaks (n = 44; see Gottselig et al. [20]). The box plots show the lower quartile, median and upper quartile values. Whiskers include the adjacent values in the data up to values within one time the interquartile range. Outliers, displayed with ‘.’ are values beyond the ends of the whiskers. The notch indicates the 95% confidence interval of the median. *p<0.05: significant difference between baseline and altitude and between the first and second night (post-hoc paired t-test, whenever factor Altitude and/or Night were significant in the mixed model ANOVA with factors Altitude, Night and Order). N1, N2: night 1 and 2 at higher altitude.
Table 2.
Changes in spectral variables at moderate altitude.
Table 3.
Correlations between spectral power and breathing variables.