Specific associations between heart rate variability and motor domains in children with attention-deficit/hyperactivity disorder: a comparative study

Objective This study compared children with Attention-Deficit/Hyperactivity Disorder (ADHD) and typically developing (TD) controls on heart rate variability (HRV) and motor proficiency, and examined their combined role in predicting ADHD symptom severity. Methods Twenty-nine children with ADHD and 33 TD children, matched for age and sex, underwent assessment. ADHD symptoms were assessed using the Strengths and Weaknesses of ADHD Symptoms and Normal Behavior (SWAN) scale, motor skills were evaluated using the Movement Assessment Battery for Children-2 (MABC-2), and resting-state HRV was recorded via a 5-minute electrocardiogram. Results The ADHD group demonstrated significantly poorer performance across all MABC-2 domains (fine motor, coordination, balance, total score; all P < 0.05). They also exhibited altered autonomic nervous system function, evidenced by significantly lower log-transformed Root Mean Square of Successive Differences and Standard Deviation of Normal-to-Normal Intervals, and a higher log-transformed LF/HF ratio (all P < 0.05). Correlation analyses revealed significant associations between motor coordination and HRV indices (logSDNN, logRMSSD). Hierarchical regression analysis identified logSDNN as a significant independent predictor of ADHD symptom severity, even after controlling for age, sex, and motor abilities. Conclusion Children with ADHD show concurrent deficits in motor skills and autonomic regulation. HRV, particularly SDNN, serves as a robust physiological marker for symptom severity, suggesting that integrated assessment of motor and autonomic function provides a more comprehensive understanding of ADHD.