To ascertain the relationship of non-randomness index with autonomic function, we estimated the partial correlation between non-randomness index and standard HRV variables, controlling for age and BMI (Table S3) . A weak but significant positive correlation of the non-randomness index with the LF/HF ratio was found (r = 0.234, p = 0.001), whereas negative correlations were found with RMSSD (r = 20.274, p,0.001) and pNN50 (r = 20.279, p,0.001).