Vagal Efferent Decline Drives Vocal Fold Extracellular Matrix Dysfunction and Systemic Inflammaging: A Testable Bottom‑Up Longevity Hypothesis

We hypothesize that age‑related loss of vagal efferent output directly drives vocal fold extracellular matrix (ECM) dysfunction by disabling the cholinergic anti‑inflammatory pathway, thereby permitting unchecked NF‑κB signaling in local fibroblasts and immune cells. This leads to excess matrix metalloproteinase activity, reduced tissue inhibitor of metalloproteinases, abnormal collagen cross‑linking, elastin fragmentation and hyaluronan depolymerization, which together raise vocal fold stiffness and impair vibratory function. Because the vocal fold receives dense vagal innervation that controls muscle tone, vascular perfusion and immune modulation, its ECM state serves as a read‑out of peripheral autonomic health. Consequently, measurable changes in vocal fold viscoelasticity (e.g., via shear‑wave elastography) should parallel systemic inflammaging markers such as circulating IL‑6, TNF‑α and nitro‑tyrosine, and predict mortality risk independent of traditional frailty indices. Mechanistically, vagal motor neurons release acetylcholine onto α7 nicotinic acetylcholine receptors on macrophages and fibroblasts, suppressing NF‑κB translocation and limiting pro‑inflammatory cytokine transcription. With age, myelinated vagal axon area declines (r = –0.74)【2】, decreasing ACh release and weakening this brake. Simultaneously, age‑related Schwann cell atrophy and delayed Wallerian degeneration impair axonal regeneration【6】, compounding the loss of efferent tone. The resulting cytokine surge activates fibroblast‑derived TGF‑β1/Smad signaling, driving collagen I/III overproduction and lysyl oxidase–mediated cross‑linking, while reactive oxygen species fragment elastin and hyaluronidase‑2 degrades hyaluronan, a key lubricant for mucosal wave propagation. Evidence from C. elegans shows that neuronal control of intestinal lipid metabolism precedes peripheral metabolic shifts【4】, supporting the notion that central neural decay can dictate peripheral tissue aging. Moreover, anterograde transport of pathogenic proteins via vagal preganglionic fibers【5】 demonstrates that the brain can exert direct deleterious effects on peripheral organs, a mechanism that may extend to ECM‑altering enzymes. We propose a falsifiable test: administer daily transcutaneous vagus nerve stimulation (tVNS) to aged mice (20‑24 mo) for eight weeks and compare vocal fold histology, biomechanical testing, and HA content to sham‑stimulated controls. Predicted outcomes: tVNS‑treated mice will show (1) reduced vocal fold collagen cross‑linking (hydroxyproline assay), (2) higher elastin integrity (Verhoeff stain), (3) restored HA molecular weight (HPLC), (4) lower vocal fold shear modulus (elastography), and (5) decreased serum IL‑6 and TNF‑α. If tVNS fails to improve any of these parameters, the hypothesis that vagal efferent loss causally drives vocal fold ECM aging is falsified. In parallel, a longitudinal human cohort could assess whether baseline vocal fold stiffness predicts incident cardiovascular events after adjusting for age, sex, smoking and baseline CRP, with tVNS intervention arms testing whether improving vocal fold mechanics reduces event rates. Positive results would reposition vagal efferent integrity as a upstream driver of peripheral aging and justify a bottom‑up longevity stack that prioritizes neural‑targeted therapies before microbiome‑centric approaches.