Table 5

 Crude risk ratios (RR) of developing respiratory symptoms† according to characteristics at baseline in asymptomatic subjects at baseline (univariate analyses)

CharacteristicsNo of subjects with incident respiratory symptomsRR (95% CI)
AHR, airway hyperresponsiveness; PC20, concentration of methacholine provoking a 20% fall in FEV1; RR, risk ratio; CI, confidence interval.
*p<0.05; **p<0.01; ***p<0.001.
†At least two of the following symptoms: wheezing, shortness of breath, chest tightness, cough, respiratory complaints upon exertion.
‡Skin reaction to two or more common aeroallergens.
§Urticaria, eczema, or hay fever.
AHR (PC20 ⩽8 v>8 mg/ml)136.02 (2.80 to 12.92)***
Current smoking30.73 (0.21 to 2.48)
Atopy‡232.38 (1.26 to 4.50)*
Atopic diathesis§91.13 (0.52 to 2.46)
Self-reported rhinitis
    Non-specific314.11 (2.08 to 8.11)***
    To animals234.66 (2.45 to 8.89)***
    To pollen173.03 (1.56 to 5.88)**
Ownership of a pet at any time411.24 (0.36 to 4.24)
Family history of asthma142.29 (1.15 to 4.56)*