Table 1

Selected sleep stage variables in healthy controls and chronic fatigue syndrome patients without sleep abnormalities
	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 ± 8^a
Sleep structure
Time in bed, minutes	453 ± 33	438 ± 42
Total sleep time, minutes	385 ± 39	351 ± 54^a
Sleep efficiency^b, percentage	85 ± 8	80 ± 10^a
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 ± 17^a
Wakefulness plus stage 1, minutes	96 ± 43	94 ± 35
Stage 2, minutes	225 ± 36	198 ± 33^a
Stage 3, minutes	29 ± 20	46 ± 23^a
Stage 4, minutes	5 ± 11	10 ± 15
Slow-wave sleep (stage 3 + 4), minutes	34 ± 26	56 ± 34
Stage REM, minutes	84 ± 25	64 ± 26^a
Sleep latency^c, minutes	16 ± 18	26 ± 26
REM latency^d, minutes	105 ± 49	127 ± 65
Median duration of sleep runs, minutes	15.6 ± 18.4	8.9 ± 5.7^a
Likert scale (0–15.5)
Sleepiness
Evening	6 ± 4	9 ± 5^a
Morning	1 ± 2^e	8 ± 4^a
Fatigue
Evening	4 ± 4	11 ± 3^a
Morning	2 ± 2^e	9 ± 4^a
Pain
Evening	1 ± 2	7 ± 5^a
Morning	0 ± 1	7 ± 5^a
Feeling blue
Evening	1 ± 2	2 ± 2
Morning	0 ± 0^e	1 ± 3^a

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.
Togo et al. Arthritis Research & Therapy 2008 10:R56 doi:10.1186/ar2425