The effect of aging on mastication and swallowing parameters according to the hardness change of solid food.

As part of the aging process, multiple oral physiologic changes occur and these changes may cause individuals to reduce food intake or switch the types of food texture. Thus, the need to develop food products for the elderly has increased. To evaluate the suitability of the food products for the elderly, the evaluation method should be verified and it is important to identify the parameters of mastication and swallowing. Therefore, the purpose of this study was to compare the differences of mastication and swallowing parameters between the young adults and the elderly depending on the varying hardness of rice food product. Subjects included 20 young adults and 40 elderly and bolus transit times of video-fluoroscopic swallowing study (VFSS) were used. Four types of rice products with different hardness were provided including cooked rice, soft-boiled rice, rice gruel and thin rice gruel. In the elderly group, the chewing number, oral processing time, post-faucial aggregation time, valleculae aggregation time (VAT), first subsequence duration and total duration were significantly different according to the changes in food hardness. Of the bolus transit times, the VAT and the second subsequence duration (S-S2) were significantly different between the two groups. These results suggest that VAT and S-S2, key VFSS parameters, as well as the chewing number and total duration are useful tools for evaluating the effect of aging on mastication and swallowing of solid foods. PRACTICAL APPLICATIONS: In Korea, the aging population is rapidly increasing. According to recent surveys, a large number of elderly Koreans have reported chewing difficulties and many of them are in the state of under-nutrition. As aging progresses, multiple physiologic changes occur in mastication and swallowing functions. These changes may cause individuals to reduce their food intake or switch to soft food products. Therefore, the development of texture-modified food products for the elderly is needed and they should be developed based on the understandings of the physiology of mastication and swallowing according to different rheological properties of food products consumed in Korea, which are quite different from those of the western countries. In this study, we compared the differences of mastication and swallowing parameters between the young adults and the elderly depending on the varying hardness of rice food product.