TABLE 5.

Multinomial regression analysis for patients who live closer to major roads than highways, for outcomes of three classes of airway hyper-responsiveness with reference to the normal group (PC₂₀ >16 mg/mL [n=1201])

PC20 class   Independent variables	B	P	OR (95% CI)
Severe (n=84)
Age, years	−0.04	<0.010	0.96 (0.94–0.97)
Ambient temperature, °C	−0.01	0.282	0.99 (0.96–1.01)
Relative humidity, %	0.01	0.206	1.01 (0.99–1.03)
FEV1, % predicted	−0.10	<0.010	0.90 (0.88–0.92)
Taking ICS*	1.13	<0.010	3.08 (1.68–5.65)
Taking LABA	−0.10	0.762	0.90 (0.46–1.76)
Female	0.86	0.001	2.37 (1.41–3.99)
Within 500 m of industry	−0.62	0.130	0.54 (0.24–1.20)
Within 200 m of major roads	−0.16	0.510	0.85 (0.53–1.37)
Moderate (n=214)
Age, years	−0.01	0.019	0.99 (0.98–1.00)
Ambient temperature, °C	0.00	0.844	1.00 (0.98–1.01)
Relative humidity, %	0.01	0.224	1.01 (0.99–1.02)
FEV1, % predicted	−0.07	<0.010	0.93 (0.92–0.94)
Taking ICS*	0.75	0.001	2.11 (1.37–3.24)
Taking LABA	0.07	0.770	1.08 (0.66–1.74)
Female	0.92	<0.010	2.52 (1.77–3.58)
Within 500 m of industry	−0.04	0.859	0.96 (0.59–1.55)
Within 200 m of major roads	0.36	0.032	1.43 (1.03–1.99)
Mild (n=414)
Age, years	−0.01	0.014	0.99 (0.98–1.00)
Ambient temperature, °C	−0.01	0.255	0.99 (0.98–1.00)
Relative humidity, %	0.01	0.316	1.00 (1.00–1.01)
FEV1, % predicted	−0.04	<0.010	0.96 (0.95–0.97)
Taking ICS*	0.37	0.030	1.45 (1.04–2.03)
Taking LABA	0.08	0.684	1.09 (0.73–1.62)
Female	0.66	<0.010	1.93 (1.49–2.49)
Within 500 m of industry	−0.28	0.169	0.76 (0.51–1.13)
Within 200 m of major roads	−0.05	0.695	0.95 (0.75–1.21)

^*Fluticasone equivalent. FEV₁ Forced expiratory volume in 1 s; ICS Inhaled corticosteroid; LABA Long-acting beta₂-agonist; PC₂₀ Provocative concentration of methacholine causing a 20% decline in FEV₁