Abstract
With aging, there is a generalized decrease in mucosal sensitivity. Such decreased sensitivity may contribute to swallowing problems in the elderly. This study was designed to compare the effects of stimulation of the pharyngolaryngeal region (PL) on voluntary swallowing between young (23-37 years, n = 18) and elderly (60-84 years, n = 23) healthy subjects. Water or 0.3 M NaCl solution was delivered into the PL through a fine tube at 0.2-5.0 ml/min. Water stimulates water receptors in the PL and 0.3 M NaCl inhibits them. Each subject was instructed to repeat swallowing as fast as possible. Swallowing intervals (SIs) between two consecutive swallows were measured. Values of SI with weak stimulation (0.3 M NaCl at 0.2 ml/min slow infusion rate) varied greatly in subjects and the values in the elderly did not differ from those in the young, suggesting that the ability of swallowing center to perform repetitive voluntary swallowing varies among subjects and that the ability to swallow in the elderly does not differ from that in the young. In the young and elderly, SIs were shorter in the case of water infusion than in the case of 0.3 M NaCl (water effect), and increasing infusion rate shortened SIs (mechanical effect). Sensory effects (water and mechanical effects) decreased in the elderly. Diminution in sensitivity of the PL with increasing age might be a contributing factor in the development of dysphagia and aspiration in the elderly. [J Physiol Sci. 2008;58 Suppl:S167]
