What is the evidence on the link between gastroesophageal reflux disease (GERD) and asthma, and cough due to GERD?
Microaspiration of the gastroesophageal refluxate into the airways is an important mechanism of airway symptomatology (cough, wheeze) secondary to GER. But with regard to reflex mechanisms inducing cough and or bronchospasm without micro- or macroaspiration, there is evidence for the presence of an active vagally mediated esophageal-bronchial reflex. Instillation of acid into the lower esophagus has been demonstrated to increase airway resistance and result in cough in the absence of radiologic evidence of aspiration. This response is abolished with blockade of afferent signaling from the lower end of the esophagus. The tracheobronchial tree and esophagus share origins from an embryologic standpoint with autonomic innervation through the vagus nerve [Sontag and Harding, 2006].
Sontag SJ and Harding SM. Gastroesophageal reflux and asthma. GI Motility Online 2006 http://www.nature.com/gimo/contents/pt1/full/gimo47.html
E.S Prakash 