text: Clinical characterization of dysautonomia in long COVID 19 patients Increasing numbers of COVID 19 patients continue to experience symptoms months after recovering from mild cases of COVID 19 Amongst these symptoms several are related to neurological manifestations including fatigue anosmia hypogeusia headaches and hypoxia However the involvement of the autonomic nervous system expressed by a dysautonomia which can aggregate all these neurological symptoms has not been prominently reported Here we hypothesize that dysautonomia could occur in secondary COVID 19 infection also referred to as long COVID infection 39 participants were included from December 2020 to January 2021 for assessment by the Department of physical medicine to enhance their physical capabilities 12 participants with COVID 19 diagnosis and fatigue 15 participants with COVID 19 diagnosis without fatigue and 12 control participants without COVID 19 diagnosis and without fatigue Heart rate variability HRV during a change in position is commonly measured to diagnose autonomic dysregulation In this cohort to reflect HRV parasympathetic sympathetic balance was estimated using the NOL index a multiparameter artificial intelligence driven index calculated from extracted physiological signals by the PMD 200 pain monitoring system Repeated measures mixed models testing group effect were performed to analyze NOL index changes over time between groups A significant NOL index dissociation over time between long COVID 19 participants with fatigue and control participants was observed p 0 046 A trend towards significant NOL index dissociation over time was observed between long COVID 19 participants without fatigue and control participants p 0 109 No difference over time was observed between the two groups of long COVID 19 participants p 0 904 Long COVID 19 participants with fatigue may exhibit a dysautonomia characterized by dysregulation of the HRV that is reflected by the NOL index measurements compared to control participants Dysautonomia may explain the persistent symptoms observed in long COVID 19 patients such as fatigue and hypoxia Trial registration The study was approved by the Foch IRB IRB00012437 Approval Number 20 12 02 on December 16 2020 