Table 3.

Agreement between sleep parameters measured by polysomnography (PSG), Zmachine, Fitbit, and sleep logs.

Comparison		r	P value	ICCa	F test	95% CI (min)	95% CI (max)	P value
Total sleep time
	PSG vs Zmachine	0.46	<.001	0.46	2.7	0.24	0.63	<.001
	PSG vs Fitbit	0.09	.47	0.08	1.2	–0.13	0.29	.24
	Sleep logs vs PSG	0.28	.03	0.23	1.68	0.001	0.45	.02
	Sleep logs vs Zmachine	0.27	.03	0.24	1.65	–0.001	0.45	.03
	Sleep logs vs Fitbit	–0.02	.88	–0.01	0.96	–0.18	0.18	.56
Wake after sleep onset
	PSG vs Zmachine	0.45	<.001	0.39	2.59	0.13	0.59	.002
	PSG vs Fitbit	0.25	.047	0.18	1.44	–0.07	0.41	.08
	Sleep logs vs PSG	0.35	.006	0.33	1.95	0.08	0.53	.005
	Sleep logs vs Zmachine	0.27	.03	0.24	1.71	0.01	0.46	.02
	Sleep logs vs Fitbit	0.09	.51	0.05	1.09	–0.21	0.29	.36
Sleep efficiency
	PSG vs Zmachine	0.50	<.001	0.40	2.93	0.09	0.62	.006
	PSG vs Fitbit	0.13	.31	0.10	1.27	–0.11	0.32	.18
	Sleep logs vs PSG	0.31	.02	0.19	1.68	–0.04	0.41	.05
	Sleep logs vs Zmachine	0.27	.03	0.24	1.67	0.004	0.46	.02
	Sleep logs vs Fitbit	–0.04	.79	–0.02	0.93	–0.16	0.15	.61

^aICC: interclass correlation coefficient.