Swallowing function and oral sensation in young and elderly humans

Objectives: There is a generalized decrease in oral mucosal sensitivity with advancing age. Such decreased sensitivity may contribute to swallowing problems in the elderly. The aim of this study was to compare the effects of stimulation of the pharyngolaryngeal region (PL) on voluntary swallowing in young and elderly healthy subjects.

Methods: Young subjects (mean age, 26.3 years; range, 23-37 years; 13 males and 8 females) and elderly subjects (mean age, 70.1 years; range, 60-84 years; 10 males and 13 females) were enrolled in this study. 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.

Results: SIs with weak stimulation (0.3 M NaCl at 0.2 ml/min slow infusion rate) varied greatly among subjects, suggesting that the ability of the swallowing center to perform repetitive voluntary swallowing varies among subjects. With this weak stimulation, SIs in the elderly did not statistically differ from those in the young (P > 0.05), suggesting that the ability to swallow in the elderly does not differ from that in young people. In general, 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). We found that the magnitudes of sensory effects (both water and mechanical effects) were lower in the elderly subjects than in the young subjects.

Conclusion: Diminution in sensitivity of the PL with increasing age might be a factor contributing to the development of dysphagia and aspiration in the elderly.