TABLE 3.

Results of multivariate linear regression analyses showing the relationship between the dependent variable (PC₂₀) and the independent variables including distance from major roads and highways

Independent variables	Highways (n=70)			Major roads (n=712)
	B	P	95% CI	B	P	95% CI
Unadjusted model
Distance from highways and major roads	0.021	0.942	−0.560 to 0.603	−0.003	0.949	−0.085 to 0.079
Adjusted model
Age, years	−0.01	0.208	−0.022 to 0.005	0.006	0.000	0.003 to 0.009
FEV1, % predicted	0.012	0.136	−0.004 to 0.027	0.016	0.000	0.012 to 0.020
Female	−0.293	0.168	−0.713 to 0.127	−0.115	0.058	−0.234 to 0.004
Taking inhaled corticosteroids*	0.057	0.815	−0.427 to 0.540	−0.223	0.002	−0.366 to −0.080
Taking long-acting beta2-agonists	−0.274	0.299	−0.797 to 0.249	0.087	0.290	−0.074 to 0.249
Temperature, °C	0.010	0.329	−0.010 to 0.030	0.002	0.513	−0.003 to 0.007
Relative humidity, %	0.010	0.272	−0.008 to 0.027	−0.003	0.160	−0.008 to 0.001
Living within 500 m of industry	0.587	0.112	−0.140 to 1.313	0.078	0.368	−0.092 to 0.248
Distance from highways and major roads	0.187	0.542	−0.425 to 0.800	0.005	0.899	−0.074 to 0.084

^*Fluticasone equivalent. FEV₁ Forced expiratory volume in 1 s; PC₂₀ Provocative concentration of methacholine causing a 20% decline in FEV₁