Table 2.

Study Sample Sleep Characteristics Stratified by Insomnia (n=399).

	Total	No Insomnia	Insomnia
N (%)	399	247 (61.9)	152(38.1)
Habitual sleep time, hours	7.1±0.9	7.2±0.8*	6.9±0.9
Most of time satisfied with sleep, N (%)	269(67.4)	203(82.2)**	66(43.4)
Difficulty getting back to sleep, N (%)	53(13.3)	0	53(34.9)
Difficulty falling sleep, N (%)	46(11.5)	0	46(30.3)
Early morning awakenings, N (%)	59(14.8)	0	59(38.8)
Repeated nocturnal awakenings, N (%)	111(27.8)	0	111(73.0)
Nap >1 time per day	239 (59.9)	141 (57.1)	98 (64.5)
PSG assessed markers of insomnia
Sleep latency, hour	0.2±0.2	0.2±0.2	20.6±19.7
Waking after sleep onset, hour	1.0±0.7	1.0±0.7	1.0±0.6
Total sleep time, hour	6.5±1.0	6.6±1.0*	6.3±0.9
Sleep efficiency, %	83.9±9.6	84.6±9.8*	82.8±9.0
% of Stage REM Sleep	18.1±6.1	18.2±5.8	17.8±6.5
% of stage 1 sleep	9.9±6.3	9.9±6.1	10.0±6.7
% of stage 2 sleep	64.2±9.0	64.0±8.41	64.6±9.9
% of stage3/4 sleep	7.7±7.2	7.9±7.1	7.5±7.3

Continuous variables were presented as Mean± standard deviation.

REM, rapid eye movement.

^*P <0.05 for comparison between not-insomnia and insomnia groups.

^#No. of symptoms was treated as continuous variable.

^##Symptom-days per month can range from 0 (no symptoms reported) to 100 (=4*25, i.e., all four insomnia symptoms reported as “almost always”)

^**P <0.01 for comparison between not-insomnia and insomnia groups.