Modulation of heart rate and heart rate variability during animal-assisted treatment of patients in a minimally conscious state: A randomized controlled crossover study

BACKGROUND: Animal-assisted treatment (AATx) is a promising and increasingly used approach in neurorehabilitation, yet its psychophysiological effects remain largely unexplored. Patients in a minimally conscious state (MCS) show severely altered consciousness with minimal but definite behavioral signs of awareness. Because behavioral assessment in this population is limited, psychophysiological measures such as heart rate (HR) and heart rate variability (HRV) may offer valuable insights into autonomic regulation during therapy. AIM: The present study investigated whether AATx influences HR and HRV compared to treatment as usual (TAU). METHODS: A randomized controlled crossover design with repeated measures was conducted. HR and HRV data were recorded using an Empatica E4 wristband, and linear mixed-effects models were fitted for each outcome variable. The analytic sample included twenty-one patients with MCS who completed at least one of the four sessions. RESULTS: We found a significant decrease in mean HR (estimate = -12.75, p =.041) and a significant increase in the standard deviation of normal-to-normal intervals (SDNN) (estimate = 15.76, p =.020) during AATx compared to TAU from the pretreatment to the posttreatment phase, indicating enhanced parasympathetic activation and greater autonomic flexibility. Other HRV parameters revealed no significant effects of AATx, though trends were consistent with the hypotheses. CONCLUSIONS: These findings provide preliminary physiological evidence that AATx can modulate autonomic activity in MCS patients. Despite limitations related to sample size and recording quality, the results highlight the potential of AATx as an emotionally engaging intervention in early neurorehabilitation.