UTRECHT – Obesity in childhood may be associated with a higher risk of asthma, a Dutch study suggests.

In the study, which included 3,756 children and was published the Journal of Allergy and Clinical Immunology, participants had an increased risk of bronchial hyperresponsiveness or dyspnoea at the age of 8 years if they had a high body mass index (BMI) at 6 to 7 years of age.

However, the association was only confirmed for a high BMI and symptoms of dyspnoea or signs of bronchial hyperresponsiveness (as assessed by methacholine challenge). Being overweight did not seem to put the children at higher risk of wheezing or of being prescribed inhaled corticosteroids.

A high BMI was defined as greater than the 85th percentile of the Dutch age-related, sex-specific references. Children with a high BMI at an earlier age who subsequently normalised their weight did not appear to be at increased risk for bronchial hyperresponsiveness or dyspnoea.

In this study of children whose mothers had been recruited from the general population during pregnancy, the prevalence of “asthma symptoms” was 14% at the age of 8 years, explained principal investigator Dr Salome Scholtens from the Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands.

Is it really asthma?

One explanation for the findings may be that, in patients with asthma, dyspnoea caused by obesity and poor fitness could be interpreted as exercise-induced asthma, comments Dr Richard M. Schwartzstein, Department of Medicine, Beth Israel Medical Center, Boston, Massachusetts, in an accompanying editorial: “The Dutch study did not establish a significant relationship between wheezing and an increased BMI”.

Asthma may indeed be more prevalent in overweight children. However, it might not be obvious which condition was present first - or the association might be bidirectional. Dr Schwartzstein then asks if it was possible that asthma was leading to a sedentary existence and causing a high BMI, rather than obesity causing asthma.

Dyspnoea may be an unspecific symptom. However, the relationship of high BMI at age 6 to 7 years with bronchial hyperresponsiveness at age 8 years supports the association of obesity with asthma, but the directionality of the relationship still remains uncertain, concludes Dr Schwartzstein.