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Musculoskeletal and Sports Medicine

Differences in Heart Rate Variability in Individuals with mTBI

Thursday, October 23, 2025
12:45 PM - 2:15 PM MT
Location: Original Research Theater
Disclosure(s):
Akbarali Nabi, DO: No financial relationships to disclose
Flynn McGuire, MD: No financial relationships to disclose
Background and/or Objectives: Abnormalities in autonomic regulation are historically reported in patients with mild traumatic brain injuries (mTBI, concussions). However, prior studies draw on heterogenous samples, often without acuity consideration. Goal of this study was to focus on individuals with acute mTBI and to determine if there are any identifiable metrics in autonomics, compared to a healthy control group, specifically with heart rate variability.

Design: Tilt table testing was performed in individuals with mTBI < 14 days of injury and age-/sex-matched health controls; HRV metrics were calculated in resting and head-up tilt phases to determine if significant between-group differences exist. HR was also evaluated as a percentage of maximum heart rate (% max HR) at predefined time points during tilt table testing, including supine and upright positions (1, 2, 5 min supine, 1, 2, 5,10 min upright, 1, 2 min supine again, and HR at end of test). Kubios was utilized to calculate these HRV variables. Mann-Whitney U tests calculated to compare mTBI vs control results.

Setting : Outpatient clinic, research lab.

Participants : Acute mTBI individuals = 12; Healthy control = 4

Interventions: Tilt Table testing

Main Outcome Measures: HRV metrics: SDNN, RMSSD, LF/HF ratio, HR/maximum heart rate (% max HR).

Results: The reported sample consists of 4 controls, and 12 acute mTBI participants. There were no statistically significant differences in supine HR (p = 0.549), RMSSD (p=0.163), LF/HF ratio (p=0.245), or pNNXX (p=0.202) between mTBI and control groups. However, noted significant difference in supine SDNN between mTBI v control (p = 0.009). No significant differences were seen in upright values.

Conclusions: We found evidence of reduced HRV (SDNN) in individuals with mTBI compared to controls. Findings support prior reports of altered HRV in mTBI, which are detectable in this study during the acute phase post-mTBI injury. Larger group sizes and longitudinal investigation are needed to determine if these changes resolve with symptomatic recovery.