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We read with interest the recent paper by Shaaban et al1 who report a negative relationship between bronchial hyperresponsiveness (BHR) and physical activity. Several hypotheses are invoked to explain this association, including a suggestion that physical activity reduces bronchial inflammation by altering airway physiology.
Their major hypothesis is that obesity reduces physical activity and that it is this reduction in physical activity which causes, in some mysterious way, the increase in BHR observed. Their proposed mechanism—that this lack of exercise is associated with a decrease in deep inspiration—is truly breathtaking.
We suggest a much more obvious explanation, which is supported by the published evidence. In our recent survey reported in Thorax2 we demonstrated a highly significant association of body mass index with chronic cough. Other associations observed in this study infer that the cough of obesity is reflux in nature. If obesity leads to reflux-related respiratory symptoms, can this form of upper airway reflux cause BHR?
Unfortunately, Shaaban et al1 do not provide us with any information concerning the incidence of classic reflux symptoms in their population. In a study of patients with dyspepsia and endoscopically proven gastro-oesophageal reflux by Bagnato et al,3 over one-third had significant BHR. These subjects had no personal/family history or symptoms suggestive of asthma.
However, about two-fifths of patients in the study by Shaaban et al had asthma-like symptoms, defined as wheeze and sedentary breathlessness. We suggest that these patients could still have reflux-related symptoms as one-third of patients with chronic reflux cough, as demonstrated by pH monitoring, complain of exertional wheeze and dyspnoea.4
With the rising levels of obesity in the population, the accurate recognition of the aetiology of the associated BHR is vital to avoid the spurious diagnosis of “late onset” asthma. Perhaps reflux asthma would be a better—but, as yet, unproven—term.
Competing interests: None.
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