Table 1

Outcome at age 3 years according to lung function at infancy (n=50)

Abnormal* LFNormal LF
(n=37)(n=13)p Value
Median (range) age (years)3.1 (2.8–3.6)3.1 (3.0–3.7)0.490Mann–Whitney U test
Parental smoking13 (35%)5 (38%)0.933Fisher exact test
Male25 (68%)9 (69%)0.912Fisher exact test
Airway symptoms
 Ongoing wheeze18 (49%)3 (23%)0.191Fisher exact test
 Ongoing cough/dyspnoea18 (49%)2 (15%)0.05Fisher exact test
 Ongoing airway symptoms36 (97%)4 (31%)<0.001Fisher exact test
Reported use of ICS37 (100%)6 (46%)<0.001Fisher exact test
 Regular27 (73%)4 (31%)0.018Fisher exact test
 Periodic10 (27%)2 (15%)0.480Fisher exact test
Purchase of asthma medication
 Median (IQR) ICS (mg)60 (80)0 (40)0.009Mann–Whitney U test
 Median (IQR) inhaled β agonists (mg)40 (120)0 (40)0.002Mann–Whitney U test
Skin prick test positive (n=49)10 (27%)6 (46%)0.304Fisher exact test
Oscillometry (N)2910
 Median (IQR) Rrs5 (kPa/l/s)1.2 (0.21)1.26 (0.32)0.357Mann–Whitney U test
 Median (IQR) Rrs5 (Z-score)0.43 (1.11)0.64 (1.32)0.217Mann–Whitney U test
 Median (IQR) Xrs5 (kPa/l/s)−0.40 (0.17)−0.42 (0.17)0.384Mann–Whitney U test
 Median (IQR) Xrs5 (Z-score)−0.10 (2.53)−0.54 (1.90)0.335Mann–Whitney U test
Abnormal LF§ at 3 years8/29 (28%)3/10 (30%)1.0Fisher exact test
  • Bold denotes p<0.05.

  • * Abnormal LF in infancy defined as reduced LF (specific airway conductance sGaw Z-score <−1.65).

  • Fisher exact test for dichotomous variables and Mann–Whitney U test for continuous variables. The comparisons are between abnormal and normal LF; p values are not corrected for multiple comparison.

  • Purchase of asthma medication during third year of life.

  • § Abnormal LF at 3 years of age defined as Rrs5 >1.65 SD of predicted or Xrs5 <1.65 SD.

  • ICS, inhaled corticosteroids; LF, lung function; Rrs5, respiratory resistance; Xrs5, respiratory reactance.