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Table 1 Selected sleep stage variables in healthy controls and chronic fatigue syndrome patients without sleep abnormalities

From: Sleep structure and sleepiness in chronic fatigue syndrome with or without coexisting fibromyalgia

  Healthy Chronic fatigue syndrome
Number 26 26
Age, years 38 ± 8 39 ± 8
Body mass index, kg/m2 24.4 ± 4.8 24.9 ± 5.2
CES-D score 8 ± 7 17 ± 8a
Sleep structure   
Time in bed, minutes 453 ± 33 438 ± 42
Total sleep time, minutes 385 ± 39 351 ± 54a
Sleep efficiencyb, percentage 85 ± 8 80 ± 10a
Number of arousals per hour 8.2 ± 5.2 5.7 ± 4.9
Wakefulness, minutes 51 ± 38 61 ± 32
Stage 1, minutes 44 ± 18 33 ± 17a
Wakefulness plus stage 1, minutes 96 ± 43 94 ± 35
Stage 2, minutes 225 ± 36 198 ± 33a
Stage 3, minutes 29 ± 20 46 ± 23a
Stage 4, minutes 5 ± 11 10 ± 15
Slow-wave sleep (stage 3 + 4), minutes 34 ± 26 56 ± 34
Stage REM, minutes 84 ± 25 64 ± 26a
Sleep latencyc, minutes 16 ± 18 26 ± 26
REM latencyd, minutes 105 ± 49 127 ± 65
Median duration of sleep runs, minutes 15.6 ± 18.4 8.9 ± 5.7a
Likert scale (0–15.5)   
   Sleepiness   
Evening 6 ± 4 9 ± 5a
Morning 1 ± 2e 8 ± 4a
   Fatigue   
Evening 4 ± 4 11 ± 3a
Morning 2 ± 2e 9 ± 4a
   Pain   
Evening 1 ± 2 7 ± 5a
Morning 0 ± 1 7 ± 5a
   Feeling blue   
Evening 1 ± 2 2 ± 2
Morning 0 ± 0e 1 ± 3a
  1. Values are presented as mean ± standard deviation. aSignificantly different from healthy controls (P < 0.05, non-paired t test). bTotal sleep time/time in bed × 100%. cTime from lights out to sleep onset. dTime from lights out to first epoch of stage REM. eSignificantly different from evening (P < 0.05, paired t test). CES-D, Centers for Epidemiological Study-Depression; REM, rapid eye movement.