A Randomized Sham-Controlled Trial of Heart Rate Variability Biofeedback Following Traumatic Brain Injury (TBI).

Traumatic brain injury (TBI) is often associated with autonomic nervous system (ANS) dysregulation and reduced heart rate variability (HRV), potentially affecting cognition. This study tested whether HRV biofeedback (HRV-B) improved resting HRV and stress recovery in individuals with TBI compared to sham control. We also examined whether HRV changes related to physical symptoms, emotional well-being, cognitive performance, and adherence. Fifty-eight participants with TBI enrolled; 49 completed the study (HRV-B: 25, mean age 27.1; sham: 24, mean age 26.6). Participants attended five weekly sessions. Assessments included cognitive, emotional, and physical outcomes. HRV metrics (HF, LF, LF/HF, SDNN, RMSSD) were collected via electrocardiogram. The HRV-B group showed a higher LF/HF ratio at rest (F(1, 43) = 9.38, p = 0.004) and during stress recovery (F(1, 172) = 4.27, p = 0.040) than sham. A group-by-session interaction (F(1, 172) = 4.18, p = 0.04) indicated an LF/HF increase over time for HRV-B. Condition effects for HF (log), RMSSD, and SDNN at rest favored sham but disappeared after adjusting for pre-assessment values. LF (log) showed no significant effects. Both groups improved in Fluid Cognition and Total Composite scores, with no between-group differences. Anxiety and depression decreased over sessions, with greater depression improvement in HRV-B. No group effects emerged for stress or life satisfaction. HRV-B increased LF/HF ratio at rest and during stressor recovery, possibly reflecting baroreflex engagement. However, other HRV condition effects attenuated after adjusting for baseline values. Cognitive and emotional gains were observed in both groups.