Table 2.

Adjusted^* mean (standard error) sleep characteristics by napping groups

Characteristic (N = 224)	0 N = 66	1 nap N = 44	2-3 naps N = 59	4 naps N + = 55	p-value for linear trend
Actigraphy nighttime sleep duration (h)	5.83 (0.10)	6.01 (0.12)	5.69 (0.11)	5.51 (0.11)	0.008#
Actigraphy sleep efficiency (%)T	2.96 (0.04)	2.90 (0.05)	2.96 (0.05)	3.05 (0.05)	0.11
Untransformed (%)	81.70	82.83	81.70	79.88
Actigraphy sleep latency (min)T	2.85 (0.09)	2.73 (0.11)	2.68 (0.09)	2.66 (0.10)	0.13
Untransformed (min)	16.29	14.33	13.59	13.30
Epworth Sleepiness Scale	6.85 (0.48)	8.45 (0.59)	8.31 (0.51)	9.39 (0.52)	< 0.001
Pittsburgh Sleep Quality Index	6.47 (0.40)	6.42 (0.49)	6.40 (0.42)	6.52 (0.44)	0.95
Diary fatigue	0.69 (0.07)	0.67 (0.09)	0.85 (0.07)	0.98 (0.08)	0.002
Diary pain	0.53 (0.07)	0.36 (0.09)	0.44 (0.08)	0.76 (0.08)	0.03
Apnea-hypopnea Index T	2.33 (0.12)	2.04 (0.15)	2.29 (0.13)	2.16 (0.13)	0.64
Untransformed Index	9.28	6.69	8.87	7.67

^*Analyses of covariance adjusted for age, race, gender, and depressive symptoms;

^#Significant race × nap group interaction, p < 0.02;

^TVariable is transformed; untransformed means provided for those variables without adjusting for age, race, gender, and depressive symptoms.