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. Author manuscript; available in PMC: 2010 Jan 1.
Published in final edited form as: J Psychosom Res. 2008 Nov 25;66(1):51–57. doi: 10.1016/j.jpsychores.2008.08.004

Table II.

Means and standard deviations of selected sleep variables in CFS and non-CFS twins

Sleep Variable CFS Twin Non-CFS Twin
Total sleep time, minutes 395.9 (53.4) 403.9 (35.8)
Sleep latency to Stage 1, minutes 4.5 (4.0) 3.8 (4.5)
Sleep latency to Stage 2, minutes 6.3 (5.8) 5.0 (4.7)
REM latency, minutes 75.3 (51.5) 65.7 (27.0)
Stage 1, % 9.1 (2.2) 8.3 (3.7)
Stage 2, % 35.2 (8.9) 38.5 (8.1)
Slow wave sleep, % 18.4 (4.5) 20.0 (5.0)
REM, % 24.2 (5.5) 21.4 (5.8)
Sleep efficiency, % * 85.1 (8.4) 87.4 (8.0)
Time awake, minutes 56.3 (29.8) 52.4 (36.7)
Apnea-hypopnea index, events/hour 7.0 (6.6) 4.1 (3.7)
*

Total sleep time/time in bed x 100%