Table 2.

Predictors of repeated asthma exacerbations

	Bivariate model HR (95% CI)	Multivariable model HR (95% CI)
Sex, women	1.17 (0.94–1.46)	–
Age
15–45	1.00	1.00
46–69	6.00 (4.67–7.71)**	3.56 (2.64–4.81)**
≥ 70	11.2 (7.29–17.2)**	6.30 (3.91–10.1)**
Decade of inclusion
1974–1979	1.21 (0.76–1.95)	–
1980–1989	1.10 (0.72–1.68)	–
1990	1.00	–
Years since symptom debut	1.02 (1.01–1.03)**	1.02 (1.00–1.03)*
Adult-onseta	1.85 (1.41–2.43)**	1.20 (0.81–1.79)
Ever smokerb	1.57 (1.19–1.82)**	1.50 (1.20–1.88)*
Pack-yearsc	1.03 (1.02–1.04)**	1.03 (1.01–1.04)*
Previous severe exacerbation	0.68 (0.50–0.94)*	1.27 (0.89–1.82)
Daily symptoms	2.49 (1.98–3.12)**	1.56 (1.22–1.99)*
Daily β2-agonist usage, > 2	2.2 (1.74–2.78)**	1.50 (1.13–1.98)*
ICS prescribed at baseline, any dose	1.37 (1.08–1.73)*	0.93 (0.72–1.19)
Lung function
FEV1 pred. < 80%	3.04 (2.41–3.83)**	1.70 (1.29–2.25)*
FEV1/FVC ratio, < 70%	2.84 (2.28–3.55) *	1.13 (0.86–1.49)
BD reversibilityd
< 12%	–	–
≥ 12%	1.31 (0.96–1.81)	–
AHR, mg/ml
< 1	1.00	1.90 (0.99–3.67)
≥ 1 to < 2	0.65 (0.44–0.96)*	1.41 (0.72–2.76)
≥ 2 to < 8	0.56 (0.43–0.80)*	1.92 (1.02–3.60)*
≥ 8	1.01 (0.54–1.89)	1.00
Peakflow variability
< 20%	1.00	–
≥ 20%	0.84 (0.68–1.04)	–
Blood eosinophils, × 109/l
< 0.09	1.31 (0.84–2.04)	0.98 (0.60–1.59)
≥ 0.09 to ≤ 0.4	1.00	1.00
> 0.4	1.33 (1.08–1.65)*	1.29 (1.03–1.61)*
Total IgE, ≥ 150 IU/l	0.71 (0.57–0.89)*	0.99 (0.77–1.27)
Negative skin prick test, n (%)	0.36 (0.28–0.45)**	1.67 (1.25–2.23)*

Results from bivariate and multivariable cox proportional hazards (PWP) model shown as hazard ratio (95% CI)

AHR airway hyperresponsiveness, BD bronchodilator, FEV₁ forced expiratory volume in 1 second, FVC forced vital capacity, ICS inhaled corticosteroids, IU International Unit, OCS oral corticosteroids

^aAge ≥ 18 years

^bCurrent or ex-smoker

^cOnly ever-smokers

^d46 did not have data

*p-value < 0.05. **p-value < 0.001. Multivariable model: Wald Chi² = 321 Degrees of freedom = 15. p < 0.0001