Gestational age at birth and wheezing trajectories at 3–11 years

OBJECTIVE: Children born preterm have an increased risk of asthma in early childhood. We examined whether this persists at 7 and 11 years, and whether wheezing trajectories across childhood are associated with preterm birth. DESIGN: Data were from the UK Millennium Cohort Study, which recruited children at 9 months, with follow-up at 3, 5, 7 and 11 years. OUTCOMES: Adjusted ORs (aOR) were estimated for recent wheeze and asthma medication use for children born <32, 32–33, 34–36 and 37–38 weeks’ gestation, compared with children born at full term (39–41 weeks) at 7 (n=12 198) and 11 years (n=11 690). aORs were also calculated for having ‘early-remittent’ (wheezing at ages 3 and/or 5 years but not after), ‘late’ (wheezing at ages 7 and/or 11 years but not before) or ‘persistent/relapsing’ (wheezing at ages 3 and/or 5 and 7 and/or 11 years) wheeze. RESULTS: Birth <32 weeks, and to a lesser extent at 32–33 weeks, were associated with an increased risk of wheeze and asthma medication use at ages 7 and 11, and all three wheezing trajectories. The aOR for ‘persistent/relapsing wheeze’ at <32 weeks was 4.30 (95% CI 2.33 to 7.91) and was 2.06 (95% CI 1.16 to 2.69) at 32–33 weeks. Birth at 34–36 weeks was not associated with asthma medication use at 7 or 11, nor late wheeze, but was associated with the other wheezing trajectories. Birth at 37–38 weeks was not associated with wheeze nor asthma medication use. CONCLUSIONS: Birth <37 weeks is a risk factor for wheezing characterised as ‘early-remittent’ or ‘persistent/relapsing’ wheeze.