# Nocturnal autonomic activity in athletes with regular versus prolonged return to sport after sport-related concussion

## TL;DR

This study explores how autonomic activity differs at night in athletes recovering from concussions, finding that those with longer recovery times show reduced parasympathetic and sympathetic activity.

## Contribution

The study identifies potential biomarkers for prolonged concussion recovery through nocturnal autonomic activity differences.

## Key findings

- Prolonged recovery athletes had significantly lower nocturnal RMSSD compared to regular recovery athletes and controls.
- Prolonged recovery athletes exhibited fewer phasic EDA events (sleep storms) than regular recovery athletes.
- No group differences were found in symptoms or autonomic measures during recovery.

## Abstract

Sport-related concussion (SRC) is a multifaceted brain injury linked to altered autonomic activity, which may persist and contribute to prolonged recovery and persisting post-concussion symptoms (PPCS). This exploratory cross-sectional study addressed whether athletes with prolonged recovery show altered nocturnal autonomic activity after SRC, offering potential insights into PPCS and biomarkers. Nocturnal autonomic activity and concussion symptoms were evaluated and compared between 17 SRC athletes and 17 matched control athletes. SRC athletes were classified by individual return to sport (RTS) into regular RTS (< 28 days, n = 10) and prolonged RTS (≥ 28 days, n = 7). Nocturnal autonomic measures were collected during and post RTS (> 3 weeks) using a multimodal wearable device. Outcomes included heart rate (HR), HR variability (RMSSD), and electrodermal activity (EDA). No group differences in concussion symptoms, HR, RMSSD, and EDA were found during RTS. Post RTS, prolonged RTS athletes displayed significantly lower nocturnal RMSSD (p = 0.035, r = 0.612) than regular RTS athletes and controls. Additionally, prolonged RTS athletes exhibited fewer phasic EDA (sleep storms) compared to regular RTS athletes. Prolonged SRC recovery might be associated with reduced nocturnal parasympathetic (RMSSD) and phasic sympathetic (EDA) activity, after clinical symptom resolution. Further research is needed to explore whether this reflects insufficient physiological recovery or deconditioning.

The online version contains supplementary material available at 10.1038/s41598-026-43546-0.