Swallowing and the duration of the hyoid movement in normal adults of different ages.

Normal swallows were examined using ultrasound imaging. Durational data of the hyoid movement were obtained from frame-by-frame analysis. The duration of the hyoid movement of three consecutive unstimulated (= dry) swallows was compared to that of stimulated (= wet) swallows in 120 subjects equally distributed among both sexes and four different age groups. Dry swallows proved to be longer than wet ones, and the duration of both types increased with age. The first dry swallow was invariably shorter than the third one; no such difference was noted with the wet swallows. With increasing age, the oral phase was more frequently accompanied by extra hyoid gestures, and the total number of swallows produced during a 10-second period was reduced in the elderly. These differences probably do not indicate pathology, but may be explained by changes in oral sensitivity, and subclinical oral-motor changes which occur in normal subjects with increasing age.