Novel biomarkers in healthy aging: Tongue and jaw kinematics as a potential way to further explore Alzheimer’s‐induced biological changes

Abstract

AbstractBackgroundMany age‐related oral health problems, such as masticatory dysfunction and dysphagia, have been associated with Alzheimer’s Disease (AD). However, how oromotor dysfunctions in healthy aging differ from those found in AD is still largely unknown. Here, we aim to assess changes in tongue and jaw kinematics in healthy aging to understand how these biomarkers may provide early signatures of AD.MethodData were collected from two male monkeys (Macaca mulatta), one young (8 years) and one older (20 years). Using high‐resolution bilateral videoradiography (200 frames/s) and the X‐Ray Reconstruction of Moving Morphology (XROMM) workflow, we quantified the 3D position of tongue and jaw radio‐opaque markers while monkeys engaged in a natural feeding behavior. To evaluate age‐related changes, we analyzed tongue and jaw kinematics relative to specific events in the feeding cycle during 10‐s feeding trials (20‐60 trials). All protocols were approved by the University of Chicago Animal Care and Use Committee and complied with the National Institutes of Health Guide for the Care and Use of Laboratory Animals. ResultDuring chews and swallows, both monkeys exhibited cyclical tongue motions, however, the tongue motions in the older monkey were substantially less stereotyped. The distributions of x‐y‐z positions of the tongue during start/end of chews and swallows were tightly clustered in the young monkey but were more spread out in the older (Fig. 1). In addition, tongue movements in the rostro‐caudal direction lagged behind jaw movements to a greater degree in the older monkey than in the younger (Fig. 2). Indeed, in the young monkey, tongue movements in the rostro‐caudal direction were highly correlated with supero‐inferior jaw movements, with peak correlations occurring at zero lag (Fig. 3).ConclusionThese results show that tongue and jaw kinematics may change with age, particularly with regards to stereotypy of tongue movement and tongue‐jaw coordination. Understanding oromotor changes in healthy aging may serve as diagnostic measures that may be helpful in treating or delaying AD progression and in reducing the severity of debilitating oromotor dysfunctions.