Text Box: THE CHARACTERISTICS OF LONG-TERM TIME DOMAIN HEART RATE VARIABILITY IN NORMAL CHILDREN LI Y, ZHOU AQ, ZHU M, et al. Shanghai Children’s Medical Center Affiliated to Shanghai Second Medical University, China Objective: To study the characteristics of long-term time domain heart rate variability (HRV) in normal children Methods: Long-term HRV (SCL, SDNN, SDNN index, SDANN, RMSSD, Triangular index) were measured and analyzed with respect to sex and age in 266 normal children [131 boys,135 girls between 2-14 years (av8y)] and also compared with normal adult reference values Results: ①There is no significant difference in HRV between boys and girls；② Heart rate but not HRV varies with age in children；③ SDNN, SDANN, RMSSD are significantly different between children and adults, especially RMSSD Conclusions: SDANN, SDNN index reflect function of the sympathetic nervous system while RMSSD reflects parasympathetic nervous function. Our study shows that children have a more active autonomic nervous system than adults. With increasing age, autonomic nervous system function especially parasympathetic nervous function is decreased. 1882