Severe asthma exacerbation hazard ratios (HRs) from Cox proportional hazard regressions (n=59 533)
| Unadjusted HR (95% CI) | p-value | AHR (95% CI) | p-value | |
| Exposure | ||||
| SABA canisters per year | ||||
| 0 | 0.38 (0.34–0.43) | <0.0001 | 0.64 (0.56–0.75) | <0.0001 |
| 1–2 | 1.00 | (Reference) | 1.00 | (Reference) |
| 3–5 | 1.73 (1.52–1.97) | <0.0001 | 1.59 (1.4–1.82) | <0.0001 |
| ≥6 | 2.50 (2.17–2.87) | <0.0001 | 2.26 (1.96–2.60) | <0.0001 |
| Covariate | ||||
| Deprivation quintile | ||||
| 1 (least) | 1.00 | (Reference) | 1.00 | (Reference) |
| 2 | 1.07 (0.91–1.25) | 0.4335 | 1.05 (0.89–1.23) | 0.5702 |
| 3 | 1.21 (1.03–1.41) | 0.0185 | 1.14 (0.97–1.33) | 0.1055 |
| 4 | 1.32 (1.14–1.54) | 0.0003 | 1.23 (1.05–1.43) | 0.0089 |
| 5 (most) | 1.51 (1.30–1.76) | <0.0001 | 1.42 (1.22–1.65) | <0.0001 |
| Dependency quintile | ||||
| 1 (least) | 1.00 | (Reference) | 1.00 | (Reference) |
| 2 | 0.82 (0.70–0.96) | 0.0135 | 0.84 (0.71–0.98) | 0.0305 |
| 3 | 0.99 (0.85–1.15) | 0.8407 | 1.01 (0.87–1.18) | 0.911 |
| 4 | 0.93 (0.8–1.09) | 0.3596 | 0.95 (0.82–1.12) | 0.558 |
| 5 (most) | 0.89 (0.77–1.02) | 0.0958 | 0.90 (0.78–1.05) | 0.179 |
| Age group at index date | 0.98 (0.97–0.99) | <0.0001 | 0.98 (0.97–0.99) | <0.0001 |
| Male sex (reference=female) | 0.67 (0.60–0.75) | <0.0001 | 0.69 (0.62–0.77) | <0.0001 |
| Rural residence (reference=urban) | 1.67 (1.47–1.91) | <0.0001 | 1.73 (1.51–1.98) | <0.0001 |
| Number of comorbidities | ||||
| 0 | 1.00 | (Reference) | 1.00 | (Reference) |
| 1 | 1.01 (0.89–1.14) | 0.8902 | 0.98 (0.86–1.11) | 0.7211 |
| 2 | 1.05 (0.91–1.20) | 0.5219 | 1.03 (0.90–1.19) | 0.637 |
| ≥3 | 0.91 (0.77–1.07) | 0.2566 | 0.97 (0.82–1.15) | 0.7115 |
AHR: adjusted hazard ratio; SABA: short-acting β2-agonist.