Severity of adverse outcome in three periods (1997–1999, 2000–2002 and 2003–2005)
| Severity category | 2000–2002 vs 1997–1999, OR (99% CI) | 2003–2005 vs 1997–1999, OR (99% CI) | Per cent of total number of adverse outcomes |
| 1 Temporary health disadvantage, recovery without (re)operation | 0.98 (0.86 to 1.12) | 1.40 (1.24 to 1.58) | 70.1 |
| 2 Recovery after (re)operation | 1.13 (0.93 to 1.38) | 1.16 (0.96 to 1.41) | 21.6 |
| 3 (Probably) permanent damage or function loss | 1.28 (0.84 to 1.94) | 1.36 (0.91 to 2.03) | 3.1 |
| 4 Death | 0.72 (0.55 to 0.94) | 0.59 (0.45 to 0.77) | 5.1 |
| All adverse outcomes | 1.03 (0.90 to 1.17) | 1.39 (1.23 to 1.57) | 100 |
In this table, and in tables 5–7, results were adjusted for age, sex, American Society of Anesthesiologists classification and surgical complexity. All ORs are provided with 99% CI (99% CI). Groups of adverse outcomes that changed significantly (p<0.01) over time and contributed more than 5% to the overall incidence are indicated in bold.