Swallowing Dysfunction and Autonomic Nervous System Dysfunction in Alzheimer's Disease: A Scoping Review of the Evidence

OBJECTIVES: To describe, synthesize, and interpret literature on swallowing impairment (dysphagia) and autonomic nervous system (ANS) dysfunction in Alzheimer's disease (AD) and to identify gaps in the existing literature. DESIGN: Scoping review of literature covering several study designs. SETTING: Literature review. PARTICIPANTS: Individuals with AD. MEASUREMENTS: Systematic searches of the PubMed, EBSCOhost, PsychINFO, Cochrane, EMBASE, and Scopus databases were conducted. Literature was identified and organized into categories. Studies were then evaluated using the Oxford Centre for Evidence-Based Medicine Levels of Evidence criteria. After evaluation, the literature was synthesized to form conclusions and identify knowledge gaps. RESULTS: Ninety-five articles met the study criteria and were included in the review. Thirty-one studies examining dysphagia in AD provide preliminary evidence on the prevalence, nature, and treatment of dysphagia in AD; knowledge gaps were identified with respect to demographic characteristics, nature of dysphagia, functional significance, assessment, treatment, and underlying mechanisms of dysphagia in AD. Sixty-four studies of ANS dysfunction in AD were reviewed, of which 49 identified at least one variable reflecting ANS dysfunction in AD. Knowledge gaps were identified related to demographics, functional significance, and underlying neural mechanisms. No studies were found that examined both dysphagia and ANS dysfunction in AD. CONCLUSION: Current evidence indicates that swallowing impairment, as well as ANS dysfunction, may occur in AD. Potential relationships between dysphagia and ANS dysfunction in AD have not been examined. Future research should explore the possibility that swallowing and ANS dysfunction in AD are related.