Association of Autonomic Dysfunction With Long COVID: Evaluation Using Quantitative Autonomic Testing

Background: Persistent symptoms (eg, heart palpitations, lightheadedness, fatigue) despite resolution of acute COVID-19 infection is termed “long COVID syndrome” or simply “long COVID.” Long COVID is believed to be associated with autonomic dysfunction, but the nature and severity of any autonomic disturbances are not well understood. Objectives: This study sought to compare autonomic function measures in patients with long COVID, control subjects, and individuals with pure autonomic failure. Methods: Patients referred for autonomic testing were classified into 3 groups: long COVID (acute COVID-19 infection ≥12 weeks before testing), control subjects (COVID-19 negative, normal autonomic tests), and pure autonomic failure (COVID-19 negative, abnormal autonomic testing). Heart rate and blood pressure were recorded during active standing, Valsalva maneuver, respiratory sinus arrhythmia, and tilt-table testing. Results: Compared with control subjects, patients with long COVID exhibited both a greater heart rate increase and blood pressure drop with active standing and tilt-table testing (all P < 0.05). They also had lower Valsalva ratios and respiratory sinus arrhythmia values than did control subjects (both P < 0.05). Compared with pure autonomic failure patients, patients with long COVID had a greater heart rate increase but a lower drop in blood pressure with active standing and tilt-table testing and lesser respiratory sinus arrhythmia values and Valsalva ratios (all P < 0.001). After age and sex adjustment, autonomic dysfunction measures in patients with long COVID were comparable with those in the pure autonomic failure group. Further, autonomic testing abnormalities were observed in patients referred up to 40 months after infection. Conclusions: When adjusted for age and sex, patients with long COVID may demonstrate persistent autonomic dysfunction that is similar to patients with pure autonomic failure.