# Characterization of sympathicotonia in post‐covid condition (long covid) and healthy controls using long‐term electrodermal activity (EDA) follow‐up

## TL;DR

This study uses long-term electrodermal activity monitoring to explore sympathicotonia in long COVID patients and healthy controls, finding that objective measurements can detect sympathicotonia during late night hours.

## Contribution

The study introduces a novel long-term electrodermal activity analysis method using a smart ring to objectively assess sympathicotonia in post-COVID condition.

## Key findings

- EDA levels were higher during late night in individuals with orthostatic sympathicotonia.
- Self-reported symptoms did not distinguish sympathicotonia, but objective EDA measurements did.
- Long-term EDA monitoring may serve as an objective tool for detecting sympathicotonia.

## Abstract

After SARS‐CoV‐2 infection, some patients develop post‐COVID condition (PCC), often associated with sympathicotonia. This study aimed to characterize sympathicotonia in PCC patients using a novel long‐term electrodermal activity (EDA) analysis via a smart ring and evaluate its clinical applicability.

Seventeen PCC patients were recruited from a Long Covid outpatient clinic, and 18 healthy controls volunteered. PCC patients were divided based on self‐reported symptoms into those with or without sympathicotonia. A 14‐day EDA monitoring was conducted. Sympathetic nervous system (SNS) activity was expressed as a double normalized index of electrodermal activity (DNE), with higher levels indicating higher SNS activity. Orthostatic tests were performed to identify orthostatic sympathicotonia. DNE levels, representing EDA, were compared to self‐reported and orthostatic sympathicotonia.

DNE levels did not differ between PCC patients with (N = 12) or without (N = 5) self‐reported sympathicotonia or compared with nonsympathetic controls. When dividing all participants by orthostatic test results, DNE levels were lower during day (08:00–14:00; p < 0.05) but higher during late night (00:00–02:00; p < 0.05) in those with orthostatic sympathicotonia (N = 21) compared to those without (N = 14), with the 24‐h comparison significant (p = 0.022). Among PCC patients, DNE levels were higher in orthostatic nonsympathicotonic (N = 7) than orthostatic sympathicotonic (N = 10) during morning (09:00–12:00; p < 0.05), with the 24‐h comparison significant (p = 0.044).

Self‐reported symptoms did not distinguish sympathicotonia. However, individuals with orthostatic test‐identified sympathicotonia had heightened EDA, indicating increased sympathetic activity, particularly during late night. PCC was not identifiable by EDA. Long‐term EDA monitoring may provide an objective tool for detecting sympathicotonia independently of self‐reported symptoms.