Evaluation of the long-term autonomic dysfunction after the recovery of COVID-19 disease

Aims: Beyond the acute phase of the COVID-19 disease, many patients experience persistent symptoms, collectively termed "post-COVID syndrome," which includes autonomic dysfunction. Heart rate variability (HRV) is a well-established method to assess autonomic nervous system (ANS) function. This study aimed to investigate the long-term impact of COVID-19 on autonomic function through evaluating the changes in HRV. Methods: This retrospective study included 225 participants divided into two groups: 117 post-COVID patients and 108 age and gender matched controls. HRV was assessed using 24-hour Holter monitoring. Time-domain and frequency-domain indices were analyzed, including standard deviation of normal-to-normal intervals (SDNN), root mean square of successive RR interval differences (RMSSD), and low frequency (LF)/high frequency (HF) ratio. Statistical comparisons were performed using independent t-tests, Mann-Whitney U tests, and correlation analyses. Results: Post-COVID patients exhibited significantly lower HRV indices compared to controls. Time-domain metrics such as SDNN (135.7±39.5 ms vs 149.1±34.2 ms, p=0.007) and RMSSD (32.7±13.7 ms vs 37.5±14.7 ms, p=0.012) were reduced in the COVID-19 group. Frequency-domain indices, including total power (TP) and HF power, were also diminished. Correlation analysis revealed no significant association between the duration of time post-COVID (one-year follow-up) and most HRV parameters. Conclusion: Post-COVID patients experience significant autonomic dysfunction, marked by reduced parasympathetic activity and increased cardiovascular risks, with some evidence of partial recovery during sleep. Routine HRV monitoring and targeted interventions, alongside further research with larger cohorts, are crucial for better understanding of the long-term effects and improving patient outcomes.