Differences in trajectories of expiratory airflow z-scores between 8 and 25 years, 8 and 18 years, and 18 and 25 years of age contrasted between EP/ELBW and control groups and between BPD and no BPD groups within the EP/ELBW cohorts
| Flow variable | 8–25 years | 8–18 years | 18–25 years |
| Mean difference* (95% CI), P value | Mean difference* (95% CI), P value | Mean difference* (95% CI), P value | |
| EP/ELBW vs controls | |||
| zFEV1 | 0.001 (−0.009 to 0.012), 0.84 | 0.004 (−0.015 to 0.023), 0.66 | 0.004 (−0.017 to 0.026), 0.71 |
| zFVC | 0.018 (0.007 to 0.030), 0.002 | 0.028 (0.008 to 0.049), 0.007 | 0.004 (−0.017 to 0.024), 0.73 |
| zFEV1:FVC | −0.021 (−0.036 to −0.005), 0.008 | −0.030 (−0.059 to −0.001), 0.042 | 0.009 (−0.015 to 0.032), 0.47 |
| zFEF25%−75% | −0.013 (−0.024 to −0.002), 0.019 | −0.025 (−0.046 to −0.005), 0.015 | 0.015 (−0.005 to 0.036), 0.14 |
| BPD vs no BPD within the EP/ELBW cohort | |||
| zFEV1 | −0.010 (−0.022 to 0.003), 0.14 | −0.015 (−0.038 to 0.008), 0.20 | 0.007 (−0.019 to 0.032), 0.61 |
| zFVC | 0.018 (0.004 to 0.032), 0.011 | 0.031 (0.005 to 0.056), 0.018 | 0.006 (−0.018 to 0.030), 0.60 |
| zFEV1:FVC | −0.032 (−0.051 to −0.014), 0.001 | −0.057 (−0.092 to −0.021), 0.002 | 0.012 (−0.015 to 0.040), 0.37 |
| zFEF25%−75% | −0.022 (−0.036 to −0.008), 0.001 | −0.043 (−0.068 to −0.018), 0.001 | 0.016 (−0.008 to 0.040), 0.20 |
*Mean differences in trajectories (rates of change in z-scores per year of age) over the respective time periods between the groups being compared (from mixed models regression).
BPD, bronchopulmonary dysplasia; EP/ELBW, extremely preterm/extremely low birth weight; FEF25%−75%, airflow between 25% and 75% of the vital capacity.