Table 1. Sleep EEG, brain myelin (MWF), and cortical markers (n=13 at T1, n=14 at T2).
Sleep variables included time in bed (lights off to lights on), sleep duration (stages N1, N2, N3, REM scored in 20-s epochs), sleep efficiency (total sleep time expressed as a % of time in bed), sleep latency (latency to the first epoch of stage N2 sleep), wake after sleep onset (WASO; duration of wake after first occurrence of stage N2 sleep), sleep stages (% of total sleep time), SWS (slow-wave sleep as stage N3), and REM sleep (rapid eye movement sleep). Sleep cycle duration includes only the first four sleep cycles. Because subjects were awakened in the morning, the last sleep cycle could not always be completed. Thus, we applied 2 additional criteria for the computation of cycle duration as in (Kurth et al., 2010): in subjects with only 4 cycles but with a missing REM sleep episode in the last cycle, the last cycle was excluded from the comparison (2 participants at T2). Further, only sleep cycles containing a minimum of 75 epochs of NREM sleep were included. Subjects with <4.5h of recorded sleep time were excluded for the computation of time in bed, WASO, N1, N2, SWS, REM sleep, and cycle duration. Wilcoxon Signed Rank Tests were performed between baseline and follow-up. The subject assessed only at T2 was included in the presented descriptive data, yet excluded for the statistical comparison of developmental change (outermost right column).
| T1 | T2 | Developmental change p (T1 vs. T2) |
|||
|---|---|---|---|---|---|
| Mean | SD | Mean | SD | ||
| Sleep EEG | |||||
| Time in bed (min) | 625.38 | 58.02 | 568.05 | 36.66 | 0.006 |
| Total sleep duration (hh:min) | 09:14 | 00:44 | 08:23 | 00:57 | 0.02 |
| Sleep efficiency (%) | 88.71 | 4.47 | 88.46 | 7.27 | Ns (0.79) |
| Sleep latency (min) | 23.05 | 58.02 | 15.88 | 8.87 | Ns (0.37) |
| WASO (min) | 50.79 | 33.46 | 51.17 | 38.42 | Ns (0.99) |
| N1 (%) | 4.11 | 1.36 | 1.90 | 1.19 | 0.01 |
| N2 (%) | 49.51 | 5.72 | 50.34 | 4.94 | Ns (0.31) |
| SWS (%) | 20.19 | 2.89 | 26.00 | 6.76 | 0.006 |
| REM (%) | 26.19 | 3.42 | 21.76 | 6.00 | 0.006 |
| Cycle duration (%) | 90.05 | 8.68 | 113.96 | 23.91 | 0.02 |
| Myelin (MWF) Variables | |||||
| Whole brain | 0.1140 | 0.0129 | |||
| Superior longitudinal fasciculus | 0.1494 | 0.0185 | |||
| Corpus callosum | 0.1891 | 0.0189 | |||
| Optic radiation | 0.1746 | 0.0216 | |||
| Cortex Markers | |||||
| Surface area (mm2) | 4.99*10Λ4 | 9.69*10Λ3 | |||
| Gray matter volume (mm3) | 1.42*10Λ5 | 2.67*10Λ4 | |||
| Cortical thickness (mm) | 2.107 | 0.094 | |||
| Curvature | 0.1356 | 0.0051 | |||