Preterm infants have an increased rate of asthma in early childhood. The purpose of this study was to see if the likelihood of asthma persists until ages 7 and 11 years.

Patients were gathered from the UK Millennium Cohort Longitudinal Study who were born in 2000 to 2001, recruited at 9 months of age, and had follow-up interviews at 3, 5, 7, and 11 years of age. Eleven thousand six hundred ninety patients were included in the 11-year analysis. Gestational age was categorized into preterm or <32 weeks’ gestation (n = 106; mean: 28.6 weeks), moderately preterm or 32 to 33 weeks’ gestation (n = 106; mean: 32.7 weeks), late preterm or 34 to 36 weeks’ gestation (n = 618; mean: 35.3 weeks), early term or 37 to 38 weeks’ gestation (n = 2327; mean: 37.7), and term or 39 to 41 weeks’ gestation (n = 8533; mean: 40.0). Inclusion criteria required complete information on gestational age by the 9-month initial survey and then completion of the survey at 7 and 11 years old.

Surveys at 7 and 11 years of age were analyzed on the basis of the questions “Has your child ever had wheezing or whistling in the chest at any time in the past 12 months?” as well as “Is your child taking any medications on a regular basis prescribed by a doctor, which includes pills, syrups, liquids, inhalers, patches, creams, suppositories, or injections?” The answers to these questions were then compared with medications prescribed through the British National Formulary, such as bronchodilators, corticosteroids, and cromoglycate. The data were then analyzed using 4 logistic models, with the following classified wheezing trajectories: “no wheeze” present at ages 3, 5, 7 and 11 years; “early-remittent wheeze” present at 3 and/or 5 years but not thereafter; “late wheeze” present at 7 and/or 11 years but not before; and “persistent and/or relapsing wheeze” present at ages 3 and/or 5 and again at 7 and/or 11 years. Adjusted odds ratios (aORs) were calculated for each wheezing trajectory by gestational age groups, with adjustments for potential confounders in the final model, including demographic variables, maternal factors, and pregnancy-related characteristics.

Male to female distribution was similar across all age groups. A total of 85.3% of the population was white, and 14.7% were black or other minority ethnic groups. At ages 7 and 11 years, 11% of children had recent wheeze, with 5% being currently on asthma medication. A total of 15.8% of all children were classified as early-remittent wheeze, 6.7% were classified as late wheeze, 11.4% were classified as persistent and/or relapsing wheeze, and 65.8% were classified as no wheeze. Children born at <32 weeks’ gestation had an increased likelihood of asthma-related outcomes at ages 7 and 11, with 3 times the odds for current use of asthma medication (3.01 aOR at 7 years [95% confidence interval (CI): 1.25–7.28] and 2.73 aOR at 11 years [95% CI: 1.24–6.02]) and twofold increased odds for wheezing in the last 12 months (2.04 aOR at 7 years [95% CI: 1.12–3.72] and 1.64 aOR at 11 years [95% CI: 0.93–2.91]). The <32 weeks’ gestation group also had 3 to 4 times the odds for all wheezing trajectories compared with their term peers. Assessing wheezing trajectories for <32 weeks’, very preterm infants demonstrated an aOR of 2.72 (95% CI: 1.49–4.96) for early-remittent wheeze, 2.19 (95% CI: 1.04–4.62) for late wheeze, and 4.30 (95% CI: 2.33–7.91) for persistent and/or relapsing wheeze. Children born after 32 to 38 weeks’ gestation did not show statistically significant associations with wheezing or asthma medications use at age 7 or 11.

Children born at <32 weeks were at greatest risk for current asthma medication use, wheezing in last 12 months, and early-remittent wheeze, late wheeze, and persistent and/or relapsing wheeze.

Previous analysis of this birth cohort at age 3 and 5 years demonstrated a statistically significant increased likelihood of wheeze in the past 12 months for infants <32 weeks’ gestation. This study manages these infants, further examining whether the risk for asthma persists at 7 and 11 years. Although asthma history was assessed by questionnaire predominantly, the diagnosis was confirmed by a physician in medical records, and documentation of medication usage was measured. Wheezing episodes in early infancy are most often associated with viral infections, and preterm infants are at increased risk of respiratory tract infections. This may explain the higher rates of wheezing in early childhood, seen in the earlier report from this birth cohort at age 3 and 5, but their susceptibility to viral infections alone does not explain the difference seen in wheezing episodes in preterm infants at age 7 and 11 years compared with infants born at later gestational ages. The association between preterm <32 weeks’ gestation and wheeze in this study may suggest that the children experienced damage to the lungs in combination with other factors that may have a lasting effect. The researchers in this study evaluated multiple prenatal factors, such as a history of asthma, mom’s educational level, ethnicity, mode of delivery, and cigarette and alcohol use, but few postnatal risk factors for wheezing were addressed. Neonatal infections or antibiotic use, mechanical ventilation, oxygen toxicity, barotrauma, and comorbid factors could have impacted lungs at a critical period of growth and development. The authors of this article present novel descriptions of specific wheezing trajectories to better identify at what age many children may “outgrow” their wheezing. These trajectories were no wheeze (no wheeze present at ages 3, 5, 7, and 11 years), early-remittent wheeze (wheezing at 3 and/or 5 years but not thereafter), late wheeze (wheezing at 7 and/or 11 years but not before), and persistent and/or relapsing wheeze (wheezing at ages 3 and/or 5 and again at 7 and/or 11 years). This large cohort demonstrated that in addition to many long-term health consequences of prematurity, the development and persistence of asthma even through elementary school is more likely if born before 32 weeks.