Table 4.

Comparison of characteristics between participants who completed each phase of the CARDIA Sleep Study and participants who completed the Year 35 CARDIA examination

	Phase 1 (questionnaires)†		Phase 2 (devices and questionnaires)†
	Included	Excluded‡	Included	Excluded§
N	2425	594	1317	1702
	Mean (SD) or n (%)	Mean (SD) or n (%)	Mean (SD) or n (%)	Mean (SD) or n (%)
Age (years)	61.1 (3.6)	61.0 (3.7)	61.4 (3.6)*	60.8 (3.6)*
Education level (years)	15.1 (2.7)	15.3 (2.6)	15.4 (2.6)*	14.9 (2.7)*
Sex (% female)	1433 (59.1)*	302 (50.8)*	806 (61.2)*	929 (54.6)*
Race (% Black)	1053 (43.4)*	298 (50.2)*	568 (43.1)	783 (46.0)

^†See Table 1 for study components by phase.

^‡Participants who completed either phase of the Year 35 examination but did not complete Phase 1 sleep questionnaires.

^§Participants who completed either phase of the Year 35 examination but did not complete Phase 2 sleep devices and questionnaires.

^* p < .05.