Table 7

Changes over time for spirometric z-scores from linear mixed models within the preterm group, contrasting smoking and not smoking groups

Change between 8 and 18 years
VariableSmoking at 18 yearsNot smoking at 18 yearsInteraction
zFEV1 −0.40 (−0.70 to −0.10) p=0.011−0.06 (−0.17 to 0.06) p=0.36−0.35 (−0.63 to −0.07) p=0.015
zFVC0.30 (0.00 to 0.59) p=0.050.42 (0.27 to 0.57) p<0.001−0.13 (−0.48 to 0.22) p=0.47
zFEV1/FVC−1.11 (−1.59 to −0.62) p<0.001−0.92 (−1.14 to −0.71) p<0.001−0.17 (−0.68 to 0.34) p=0.51
zFEF25%–75% −0.28 (−0.61 to 0.05) p=0.09−0.02 (−0.17 to 0.12) p=0.74−0.25 (−0.59 to 0.08) p=0.14
zFEF75% −0.61 (−0.98 to −0.24) p=0.002−0.27 (−0.44 to −0.11) p=0.001−0.41 (−0.82 to 0.00) p=0.05
  • Values are mean difference (95% CI), unless otherwise stated.

  • FEF25%–75%, forced expiratory flow at 25%–75% of FVC; FEF75%, forced expiratory flow at 75% of FVC expired.