Crude and adjusted hazard ratio (HR) of a subsequent exacerbation and of death associated with each successive exacerbation, as a function of the time since the first exacerbation, estimated by Cox proportional hazards model with time-dependent covariate defining the exacerbation number and its timing
| Exacerbation sequence number | Median time to subsequent exacerbation (years) | Number with a subsequent exacerbation | Crude HR | Adjusted* HR (95% CI) | Number of deaths | Crude HR | Adjusted* HR (95% CI) |
| First (reference) | 5.4 | 33 166 | 1.0 | 1.0 (reference) | 25 953 | 1.0 | 1.0 (reference) |
| Second | 1.6 | 19 359 | 3.0 | 2.9 (2.8 to 2.9) | 9828 | 1.8 | 1.9 (1.8 to 1.9) |
| Third | 0.9 | 12 413 | 5.1 | 4.9 (4.8 to 5.0) | 5203 | 2.4 | 2.4 (2.3 to 2.5) |
| Fourth | 0.7 | 8374 | 7.3 | 6.9 (6.8 to 7.1) | 3078 | 2.8 | 2.9 (2.8 to 3.0) |
| Fifth | 0.5 | 5903 | 9.8 | 9.2 (8.9 to 9.4) | 1879 | 3.0 | 3.2 (3.0 to 3.4) |
| Sixth | 0.4 | 4316 | 11.9 | 11.2 (10.8 to 11.5) | 1207 | 3.1 | 3.3 (3.1 to 3.5) |
| Seventh | 0.3 | 3190 | 13.9 | 13.0 (12.5 to 13.5) | 872 | 3.4 | 3.6 (3.4 to 3.9) |
| Eighth | 0.3 | 2404 | 16.6 | 15.2 (14.6 to 15.9) | 645 | 3.9 | 4.2 (3.9 to 4.5) |
| Ninth | 0.3 | 1823 | 18.1 | 16.6 (15.8 to 17.4) | 470 | 3.8 | 4.3 (3.9 to 4.7) |
| Tenth or greater | 0.2 | 1403 | 25.8 | 23.5 (22.8 to 24.2) | 1445 | 4.5 | 5.2 (4.9 to 5.5) |
↵* Adjusted for age, sex, calendar time (cohort entry prior to 2000), and the modified Chronic Disease Score divided in quartiles with a fifth category to account for subjects with no or partial medication information in the year prior to cohort entry.