Rates of chronic lung disease (CLD), using the 28 day and 36 week definitions
| Year | No of survivors who received ventilation (%) | No with CLD (%) | Comparison period |
Odds ratio (95% CI) for CLD | Odds ratio (95% CI) for CLD adjusted for birth weight and gestational age |
| 28 day definition | |||||
| 1987 | 305 (46) | 75 (25) | |||
| 1992 | 365 (50) | 148 (41) | 1987 : 1992 | 2.09 (1.50 to 2.92) | 2.20 (1.47 to 3.30) |
| 1997 | 388 (47) | 162 (42) | 1992 : 1997 | 1.05 (0.72 to 1.40) | 0.72 (0.5 to 1.03) |
| 36 week definition | |||||
| 1987 | 304 (46) | 33 (11) | |||
| 1992 | 350 (49) | 92 (26) | 1987 : 1992 | 2.93 (1.90 to 4.51) | 3.04 (1.91 to 4.83) |
| 1997 | 382 (46) | 110 (29) | 1992 : 1997 | 1.13 (0.82 to 1.57) | 0.88 (0.61 to 1.26) |
Odds ratios for CLD comparing 1987 with 1992 and 1992 with 1997, both adjusted and unadjusted for changes in birth weight and gestational age, are also shown.