Table 1.
Characteristics of cases and controls in the nested case control study
| Characteristics | Severe exacerbation Number (%) | Moderate exacerbation Number (%) | ||
|---|---|---|---|---|
| Cases n = 128 | Controls n = 489 | Cases n = 598 | Controls n = 2196 | |
| Age (years, SD) * | 70.0 (12.3) | 73.0 (9.6) | 70.3 (10.5)† | 71.6 (8.9) |
| Female gender | 85 (66.4) | 328 (67.1) | 333 (55.7) | 1231 (56.1) |
| Years of follow‐up (SD) * | 2.4 (2.6) | 2.4 (2.6) | 1.6 (2.2) | 1.5 (2.1) |
| Asthma therapy | ||||
| ICS | 57 (44.5) | 235 (48.1) | 266 (44.5) | 1022 (46.5) |
| LABA | 36 (28.1)† | 66 (13.5) | 72 (12.0) | 213 (9.7) |
| LABAICS | 43 (33.6) | 141 (28.8) | 185 (30.9)† | 560 (25.5) |
| Leukotriene antagonist | 15 (11.7) | 22 (4.5) | 23 (3.8)† | 28 (1.3) |
| Methylxanthine | 24 (18.8) | 51 (10.4) | 28 (4.7) | 90 (4.1) |
| Oral steroid | 72 (56.3)† | 84 (17.2) | n/a | n/a |
| No. of SABA prescriptions (SD) * | 3.0 (2.5)† | 1.7 (1.6) | 1.6 (1.6)† | 1.2 (1.4) |
| Ocular hypertension therapy | ||||
| Non‐selective beta‐blocker | 15 (11.7) | 75 (15.3) | 84 (14.0) | 303 (13.8) |
| Selective beta‐blocker | 5 (3.9) | 10 (2.0) | 15 (2.5) | 77 (3.5) |
| Prostaglandin analogue | 84 (65.6) | 349 (71.4) | 441 (73.7) | 1598 (72.8) |
| Carbonic anhydrase inhibitor | 45 (35.2) | 131 (26.8) | 161 (26.9) | 618 (28.1) |
| Sympathomimetic | 12 (16.4) | 67 (13.7) | 48 (8.0) | 207 (9.4) |
| Miotic | 5 (3.9) | 20 (4.1) | 34 (5.7) | 89 (4.1) |
| Comorbidity | ||||
| Nasal polyps | 9 (7.0) | 24 (4.9) | 23 (3.8) | 99 (4.5) |
| BMI (SD) * | 27.4 (5.7) | 27.3 (5.3) | 28.2 (5.4)† | 27.4 (6.1) |
| Charlson comorbidity index (SD) * | 2.7 (2.0) | 2.5 (1.9) | 2.4 (1.8) | 2.5 (1.9) |
| Smoking status | ||||
| Current smoker | 13 (10.2) | 82 (16.8) | 100 (16.7)† | 229 (10.4) |
| Ex‐smoker | 66 (51.6) | 258 (52.8) | 310 (51.8) | 1131 (51.5) |
| Non‐smoker | 39 (30.5) | 129 (26.4) | 169 (28.3) | 709 (32.3) |
| Missing | 10 (7.8) | 20 (4.1) | 19 (3.2) | 127 (5.8) |
| Primary care asthma review | 51 (39.8) | 151 (30.9) | 253 (42.3) | 882 (40.2) |
| Previous asthma hospitalization | 32 (25.0)† | 20 (4.1) | 30 (5.0)† | 47 (2.1) |
| RTI 90 days prior to index date | 29 (22.7)† | 50 (10.2) | 89 (14.9)† | 129 (5.9) |
*
Continuous variables analysed with anova, otherwise categorical variable analysed using Chi‐square test.
†
Characteristics with statistically significant differences between cases and controls (P < 0.05).
BMI, Body mass index; ICS, inhaled corticosteroid; LABA, long‐acting beta2‐agonist; LABAICS, long‐acting beta2‐agonist in combination inhaler with ICS; RTI, respiratory tract infection; SABA, short‐acting beta2‐agonist; SD, standard deviation.
Severe exacerbation = asthma hospitalization. Moderate exacerbation = receipt of rescue oral steroid in primary care.