Table 3.

Effect of Secondhand Smoke Exposure on Lung Function^a

	Single Variableb		Multiple Variablec
	β	P Value	β	P Value
Smoking in the home (no secondhand smoke = 0, secondhand smoke = 1)	−0.086	.003	−0.067	.02
Age	−0.002	.11	−0.004	.03
Age at diagnosis	0.006	.01	0.008	<.001
Socioeconomic status (lowest = 1, highest = 5)	0.019	.08	0.014	.18
Race (0 = white, 1 = nonwhite)	−0.006	.30	−0.006	.36
Sex (male = 1, female = 2)	−0.007	.73	−0.011	.59

^aA total of 749 individuals had all data available and were included in all the regressions in this table.

^bLinear regressions with maximum forced expiratory volume in the first second of expiration (FEV₁) cystic fibrosis percentile as the dependent variable with the single independent variable as listed.

^cMultiple regression with maximum FEV₁ cystic fibrosis percentile as the dependent variable and the independent variables as listed.