Table 2

Risk factors for airflow limitation defined as FEV1/FVC <70% in never-smokers with and without asthma

Never-smokers with asthma
(n=2304)		Never-smokers without asthma
(n=36 798)
Age and sex-adjusted ORs (95% CI)Multivariable-adjusted ORs (95% CI)Age and sex-adjusted ORs (95% CI)Multivariable-adjusted ORs (95% CI)
Risk factors
BMI (kg/m2)0.94 (0.91 to 0.96)*0.94 (0.92 to 0.97)*0.95 (0.94 to 0.96)*0.95 (0.94 to 0.96)*
Familial predisposition for asthma0.97 (0.78 to 1.21)0.98 (0.79 to 1.23)1.26 (1.13 to 1.40)*1.29 (1.17 to 1.44)*
Asthma, hay fever, or eczema in childhood1.49 (1.20 to 1.85)*0.99 (0.76 to 1.29)1.18 (1.05 to 1.34)†1.13 (0.99 to 1.29)
Low leisure time physical activity‡0.95 (0.62 to 1.46)1.05 (0.67 to 1.64)1.21 (1.03 to 1.44)†1.44 (1.21 to 1.71)*
Low education§0.76 (0.58 to 0.99)†1.00 (0.74 to 1.34)0.77 (0.70 to 0.84)*0.83 (0.75 to 0.91)*
Low annual household income¶0.79 (0.57 to 1.10)0.89 (0.62 to 1.27)0.94 (0.84 to 1.05)1.07 (0.95 to 1.20)
Occupational exposure to dust and/or fumes0.82 (0.59 to 1.14)0.95 (0.67 to 1.35)0.86 (0.73 to 1.00)1.00 (0.85 to 1.18)
Daily exposure to passive smoking0.71 (0.53 to 0.94)†0.77 (0.57 to 1.04)0.76 (0.68 to 0.86)*0.82 (0.73 to 0.93)*
Allergy1.16 (0.88 to 1.53)0.93 (0.69 to 1.25)1.05 (0.96 to 1.15)0.99 (0.90 to 1.09)
Duration of asthma (years)1.02 (1.02 to 1.03)*1.02 (1.01 to 1.03)*NANA
C reactive protein (mg/L)1.00 (0.98 to 1.02)1.00 (0.98 to 1.03)1.00 (0.99 to 1.00)1.01 (1.00 to 1.02)
Fibrinogen (μmol/L)0.97 (0.93 to 1.01)0.98 (0.93 to 1.03)0.95 (0.94 to 0.97)*0.97 (0.95 to 0.98)*
Leucocytes (×109/L)1.03 (0.98 to 1.09)0.88 (0.76 to 1.03)0.98 (0.95 to 1.00)†0.98 (0.94 to 1.01)
Neutrophils (×109/L)1.05 (0.98 to 1.13)1.25 (1.04 to 1.50)†0.98 (0.96 to 1.01)1.02 (0.98 to 1.08)
Eosinophils (0.10×109/L)1.14 (1.08 to 1.20)*1.16 (1.09 to 1.23)*1.03 (1.00 to 1.05)†1.04 (1.01 to 1.07)†
IgE** (10 IU/mL)1.00 (1.00 to 1.00)1.00 (1.00 to 1.00)1.00 (1.00 to 1.00)1.00 (1.00 to 1.00)

  • The multivariable-adjusted models included all of the potential risk factors listed in the table. However, since measurement of IgE was only available in a subgroup, it was not included. IgE was only included in its own multivariable-adjusted model. Risk factors included in the models were dichotomous except BMI, duration of asthma and inflammatory biomarkers that were continuous.

  • *p<0.001.

  • †p<0.05.

  • ‡Low leisure time physical activity was none or light activity <2 h/week versus light activity ≥2 h/week or heavy activity ≥2 or regular exercises per week.

  • §Low education was <10 years versus ≥10 years of school attendance.

  • ¶Low annual household income was <200 000 Danish kroner versus ≥200 000 Danish kroner.

  • **Not available for all individuals.

  • BMI, body mass index; NA, not applicable.