Measuring autonomic influence on gastrointestinal contractility: development and preliminary validation of novel capsule-based indices.

The migrating motor complex (MMC) is a key feature of fasting gastrointestinal (GI) motility, but its disruption in neuropathic conditions remains poorly characterized. Wireless motility capsules (WMCs) offer a noninvasive means of collecting motility data, facilitating study of larger cohorts. We aimed to develop WMC-derived metrics to identify neuropathic dysmotility and its associations with autonomic nervous system (ANS) function. We analyzed WMC data from 98 controls and 71 people living with human immunodeficiency virus (HIV; PWH) in whom autonomic neuropathy (AN) and delayed small bowel transit time (dSBTT) are common. We studied nine contractility metrics, including established and novel metrics targeting rhythmic bursts of sustained contractile activity. Autonomic function, summarized as Modified Composite Autonomic Severity Score (MCASS), was used to draw associations with contractility measures. All contractility metrics were higher in PWH compared with controls (P ≤ 0.01 for all). Among PWH, those with AN showed the highest contractility, whereas those with dSBTT had the lowest. In controls, rhythmic bursts were more clustered, especially in the later portions of the small bowel recording, and had less variability in contraction amplitude and timing, potentially indicating greater organization. Overall, worse autonomic function was associated with higher contractility. WMC-derived metrics effectively capture fasting small bowel motility and may distinguish neuropathic patterns, which appear to progress from increased, disorganized contractility to decreased contractility as dSBTT develops. Future studies should validate these findings in other WMCs and populations to clarify their potential in advancing understanding of the pathophysiology of gut-brain-axis disorders.NEW & NOTEWORTHY This study introduces novel WMC-derived contractility indices to quantify gastrointestinal motility, enabling noninvasive characterization of neuropathic dysmotility. In PWH, hypercontractility and disorganized rhythmic bursts were observed despite autonomic neuropathy and delayed transit, suggesting a spectrum in which inefficient high-amplitude contractions initially may preserve transit before progressive delay ensues. Leveraging raw pressure data from WMC technology, these indices are linkable to extrinsic autonomic biomarkers and may advance understanding of gut-brain axis disorder pathophysiology.