Table 1.

Baseline sample characteristics

Parameter	Excessive daytime sleepiness, n = 146, mean (SD)	No excessive daytime sleepiness, n = 143, mean (SD)	P-value
Demographic
Age, years	78.0 (6.3)	77.9 (6.4)	0.9
Gender, percent female	71.9%	76.2%	0.4
Race, percent Caucasian	74.0%	74.1%	0.9
Education, percent with high school or less	37.2%	34.5%	0.6
Marital status, percent married	38.6%	41.3%	0.6
BMI, kg/m2	27.0 (4.6)	25.8 (4.7)	0.02
Sleep parameters*
Habitual sleep duration, self-report, h	6.5 (1.4)	6.8 (1.4)	0.08
Total sleep time (polysomnography sleep duration), h	5.8 (1.2)	6.1 (1.0)	0.09
Slow wave sleep, percent	6.4% (9.1)	6.9% (8.3)	0.6
REM sleep, percent	17.5% (7.2)	16.6% (6.2)	0.3
Sleep onset latency, min	18.1 (35.6)	13.7 (17.1)	0.2
Wakefulness after sleep onset, min	99.8 (63.1)	87.3 (52.0)	0.07
REM latency, min	101.2 (71.7)	113.1 (79.6)	0.2
Sleep efficiency, percent	74.9 (13.8)	78.3 (11.4)	0.03
Apnea-hypopnea index (events/h)	17.2 (21.2)	11.9 (16.2)	0.02
Arousal index (arousals/h)	23.8 (16.8)	20.6 (11.9)	0.06
NREM oxygen saturation nadir, percent	86.8 (8.9)	88.2 (7.0)	0.1
REM oxygen saturation nadir, percent	85.4 (9.5)	88.3 (6.6)	0.003
Central sleep apnea, percent	4.8%	2.1%	0.2

^*Sleep parameters were derived from polysomnography unless otherwise noted.