AGE AND AGE-RELATED DISEASE EFFECTS ON SWALLOWING

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Recent evidence suggests swallowing is affected by normal aging. Since age-specific change are not well-defined or understood, this limited knowledge complicates accurate dysphagia diagnosis in the elderly, in whom chronic debilitating diseases accompanied by swallowing problems occur with increased frequency. The long-term objective of this project is to increase understanding of the effects of normal aging on swallowing physiology in an effort to advance the diagnosis and treatment of oropharyngeal swallowing disorders in age-related disease. The proposed work will establish a normative data base of movement parameters comprising salient features of oropharyngeal swallowing in conjunction with structural brain quantification, obtained with magnetic resonance imaging, throughout the adult age interval of 45 to 95 years. One hypothesis to be tested is that oropharyngeal swallowing will differ with increasing age in terms of range, duration and direction of motion. In addressing this hypothesis, the quantification of various parameters will be expanded as will understanding of swallowing physiology and the effects of age on it. Little quantitative information on the specific parameters of oral movements during swallowing has been obtained using fluoroscopy. This is largely due to limitations inherent in fluoroscopic imaging of oropharyngeal soft tissue structures, particularly the tongue. Techniques to facilitate lingual point place tracking simultaneously with bolus tracking during fluoroscopic recording of swallowing have recently been established and a customized computer-based system has been developed to facilitate movement of soft tissue structures and provide a reliable source of kinematic measurement. These new methodologies will be used tin the proposed project. Also, the hypothesis that maximum tongue strength differs for young and old individuals and percent of maximum tongue strength used in swallowing increases with age will be tested. A pressure transducer, designed to measure tongue strength used in swallowing increases with age will be tested. A pressure transducer , designed to measure tongue strength during swallowing will be used to test the hypothesis that lingual pressure is predictive of pharyngeal kinematic parameters, bolus transit and pharyngeal kinematics in a test group of normals also will be studied. Comparison of normative data to swallowing profiles (bolus transit time, lingual pressure, and oropharyngeal kinematic measures and their interrelationships) and clinicoanatomic correlates of unilateral stroke patients with and without swallowing complaints will be studied. In this manner, another major objective, to distinguish changes in neuromotor processes and their relationship to anatomical changes in the brain that occur with normal aging from neuromotor deficiencies and clinicoanatomic correlates due to age-related disease, in this case stroke, will be addressed with specific regard to the swallowing mechanism. The relationship of aspects of swallowing physiology to nutritional parameters in normals of different ages and stroke patients also may contribute to diagnostic criteria for presence of dysphagia. The proposed examination of the interrelationships among physiologic parameters, nutritional parameters, and neurovascular correlates with normal and pathologic aging, will provide insights to the underlying mechanisms for differences found and will guide age-appropriate treatment development. Finally, soft tissue imaging and oral pressure measurement and analysis techniques will be substantially improved during the years of this project, providing better methodology and tools for future investigations of swallowing.