Table 2.

Assessment of Factors for Association with Nocturnal Asthma and Potential Differences by Race/Ethnicity

	All Subjects		African American		European American		Pint†
	OR*	95% CI	OR*	95% CI	OR*	95% CI
Age at enrollment, yr	1.02	1.02–1.03	1.03	1.03–1.04	1.02	1.01–1.03	1.000
Race/ethnicity, African American	2.95	2.61–3.34	—	—	—	—	—
Sex, female	1.61	1.43–1.82	1.64	1.43–1.89	1.91	1.30–2.00	0.940
Height, m	0.22	0.13–0.40	0.32	0.16–0.64	0.23	0.08–0.68	0.620
BMI, kg/m2	1.04	1.03–1.05	1.03	1.02–1.03	1.05	1.04–1.07	<0.001
Smoking, ever smoker	2.51	2.22–2.83	2.71	2.32–3.16	2.00	1.60–2.51	0.028
Age at diagnosis, yr	1.01	1.00–1.01	1.01	1.01–1.02	1.01	1.00–1.02	0.230
Age at diagnosis > 12 yr	1.28	1.15–1.44	1.49	1.29–1.71	1.31	1.06–1.61	0.378
Ever hospitalized, yes	2.22	1.98–2.49	1.78	1.55–2.04	2.17	1.73–2.73	0.142
FEV1, L	0.47	0.43–0.50	0.52	0.48–0.57	0.54	0.47–0.62	0.668
FVC, L	0.60	0.57–0.64	0.68	0.63–0.73	0.67	0.60–0.75	0.917
FEV1/FVC ratio	0.96	0.95–0.96	0.96	0.95–0.97	0.97	0.96–0.98	0.164
Bronchodilator reversibility	1.03	1.03–1.04	1.03	1.02–1.03	1.05	1.04–1.06	0.002

Definition of abbreviations: BMI = body mass index; CI = confidence interval; OR = odds ratio; P_int = P value from a 1 degree of freedom likelihood ratio test of the multiplicative interaction between self-reported race/ethnicity and each variable.

The outcome variable for the association analyses was nocturnal asthma defined as having any night with disrupted sleep due to asthma in the preceding 4 weeks.

^*ORs represent the univariable relationship with nocturnal asthma. These estimates reflect the effect of a one-unit increase in the variable of interest.

^†The P value for the likelihood ratio test of interaction between race/ethnicity and each variable in a bivariable model, which includes a covariate for self-reported race/ethnicity.