Effects of chronic use of thickened liquids in a rat model of aging

点击翻译按钮获取中文摘要

Abstract Swallowing disorders are highly prevalent in elderly people, including those with age-related diseases. Thickened liquids are frequently used in the treatment of swallowing disorders and have been shown to immediately reduce the chance of airway invasion. However, thickened liquids have been associated with deleterious health effects such as dehydration, urinary tract infection, and reduced quality of life. Despite their common clinical use, the long-term efficacy of thickened liquids, and their effect on swallowing kinematics, systemic hydration, and underlying biology, is not well understood. Given the rapidly increasing population of persons over 65, estimated to reach 2.1 billion by 2051, it is critical to understand the efficacy of dysphagia interventions. The overarching goal of this proposal is to contribute foundational knowledge of biological mechanisms underlying functional swallowing changes in response to a frequently used, but understudied, intervention for dysphagia management in the aging population. The proposed study will use an aging rat model to interrogate how use of thickened liquids affects swallowing kinematics, systemic hydration, and underlying biology over time. We have 3 specific aims, each with a unique hypothesis. Aim 1 will test the hypothesis that chronic use of thickened liquid textures reduces bolus speed, reduces coordination of swallowing muscles, and disrupts normal respiratory-swallow event sequencing. Aim 2 will test the hypothesis that thickened liquids result in reduced volume of fluid intake and systemic dehydration, which will be exacerbated by viscosity and age. Aim 3 will test the hypothesis that thickened liquids, in the absence of thin liquid, will slow swallowing movements, dynamically altering muscle contractile properties to include reduced tongue forces and increased contraction times in an age-dependent manner. In concert, the proportion of fast- contracting type IIb myosin heavy chain (MyHC) isoforms in the tongue will be reduced, causing an increased proportion of slower-contracting isoforms, such as type IIa and type I. This research is highly significant in that it will be the first in an aging animal model to examine the effects of thickened liquids on systemic hydration along with underlying muscle biology, kinematics, and physiology, and the relationship to clinically relevant outcome measures of swallow function. Knowledge gained from this work will lead to hypotheses for testing in clinical studies that are crucial for clinical decisions that must balance patient risk of aspiration and subsequent medical complications, against the impact of potential deleterious effects of thickened liquids on patient overall medical status and quality of life.