Children Outgrow Prematurity-Linked Increase in Asthma Prescriptions

By Will Boggs MD

NEW YORK - Premature birth is associated with an increased use of prescription asthma medication through adolescence, but this tendency disappears by young adulthood, according to a Danish National Cohort Study.

"This increased likelihood is not entirely explained by neonatal respiratory diseases, which means some other factors might be influencing the lung growth in these children," Dr. Anne Louise Damgaard, from Copenhagen University Hospital Rigshospitalet, told Reuters Health by email. "However, (and most importantly), most of them seem to outgrow this increased likelihood, perhaps due to a normalization of their lungs."

Preterm birth has previously been shown to be a risk factor for asthma-like symptoms in childhood, but some studies have suggested that children outgrow this tendency by adulthood.

Dr. Damgaard's team used data from Statistics Denmark and other national registries to reassess the association between prematurity and the purchase of prescription asthma medication as a marker for the prevalence of a persistent disease burden of asthma-like symptoms across the age span from infancy to young adulthood.

The study included nearly 1.8 million individuals, representing 84.6% of individuals born in Denmark between January 1980 and December 2009.

Compared to term newborns, those born premature were 59% to 286% more likely to use asthma medications between ages 0 and 2 years and between 21% and 73% more likely to use such medications between the ages of 12 and 17 years (with rates rising with decreasing gestational age at birth).

But by young adulthood, odds ratios for most gestational age groups were not significantly elevated, according to the February 4 PLoS ONE online report. Only those born moderately preterm (at 32-36 weeks gestation) had increased prevalence of asthma medication use at 18-24 years (a 24% increase) and 25-31 years (a 31% increase).

In the groups that were extremely preterm (23-27 weeks gestation) and very preterm (28-31 weeks gestation), acute neonatal respiratory distress contributed to the risk for asthma medications, but the risk persisted after adjustment for this factor.

"We believe that there is a correlation between neonatal respiratory diseases such as respiratory distress syndrome and especially bronchopulmonary dysplasia and the use of asthma medication in childhood," Dr. Damgaard said. "Efforts on fighting these diseases, e.g. like what we saw back in the late 1980s with the introduction of the CPAP-treatment, could probably help to bring down the need for asthma medication later in life."

"However, we also found that these neonatal diseases did not fully account for the increased risk of later asthmatic symptoms in children born preterm," she said. "Therefore, we definitely also need to look into other factors, including maternal prenatal factors, that could lead to preterm birth, low birth weight, and disturbances in lung growth."

"Finally," Dr. Damgaard said, "we must bear in mind that children born preterm are probably more likely to receive asthma medication at a lower clinical threshold, both due to the parents' health-seeking behavior and the physicians' a priori knowledge."

The study, Dr. Damgaard added, "raises questions about the before and after though: What exactly leads to this increased risk? Can we prevent it? Do the symptoms relapse in older age? How should they be managed and could they be prevented? It would be interesting to see more clinical studies on the subject, as we see a growing population of longer-term survivors of preterm birth."

Dr. Katy C. Pike recently reviewed the respiratory consequences of preterm birth. She told Reuters Health by email, "Even moderate/late prematurity, which is associated with lesser degrees of pre- and postnatal insults, appears to be associated with increased odds of needing asthma meds. Together with the observation that asthma med purchase is increased in preterm gestations even after adjusting for perinatal factors, this suggests prematurity per se may be associated with greater chance of asthma-like symptoms, possibly due to impaired lung development and function."

"If this is the case," she said, "strategies must include carefully weighing the pros and cons of early delivery, and where early delivery cannot be avoided, research attention should turn to catch-up growth and which ventilation, pharmaceutical, and nutritional strategies best support this."

Dr. Pike added, "I would say knowledge is not complete enough to prevent this problem yet, but we must be aware of preterms as an at-risk group for obstructive lung disease. They might be vulnerable in the first weeks of life to symptoms of wheeze with viruses and in later life to COPD."

This research was funded in part by Rigshospitalet Research Funds.

SOURCE: https://bit.ly/1KJwUtp

PLoS ONE 2015.

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