Transcranial direct current stimulation improves heart rate variability: A systematic review and meta-analysis

Area of Science:

• Neuroscience
• Cardiovascular Physiology

Background:

• Heart rate variability (HRV) is a critical metric for assessing autonomic nervous system (ANS) function.
• Transcranial direct current stimulation (tDCS) is an emerging neuromodulation technique.

Purpose of the Study:

• To systematically review and meta-analyze the effects of tDCS protocols on HRV parameters.
• To investigate how different tDCS parameters and conditions influence HRV outcomes.

Main Methods:

• A meta-analysis of 97 comparisons from 24 studies was conducted.
• Standardized mean difference (SMD) was used to estimate effect sizes for HRV changes between active tDCS and sham conditions.
• Moderator and meta-regression analyses explored the impact of task type, brain region, stimulation parameters, and participant characteristics.

Main Results:

• tDCS protocols significantly improved HRV (SMD = 0.400, P < 0.001).
• Anodal M1 stimulation enhanced HRV during physical stress (SMD = 1.352, P = 0.001).
• Combined polarity stimulation on the PFC improved HRV during psychological stress (SMD = 0.550, P < 0.001) and rest (SMD = 0.192, P = 0.012).

Conclusions:

• tDCS protocols show potential for improving HRV, suggesting benefits for cardiovascular ANS function.
• Optimizing targeted brain stimulation may enhance HRV patterns.