目的 研究维生素D缺乏对学龄前期肥胖儿童心脏自主神经功能的影响。方法 242例学龄前期单纯性肥胖儿童，根据血清25-羟基维生素D（VitD）水平分为VitD缺乏组（76例）、VitD不足组（83例）及VitD充足组（83例），将3组间心率减速力（DC）、心率加速力（AC）及心率变异性（HRV）进行比较；并分别将VitD不足组和缺乏组的VitD水平与DC、AC、HRV进行相关性分析。结果 DC、相邻RR间期差值的均方根（RMSSD）、低频功率（LF）以VitD缺乏组最低（P < 0.05），AC值以VitD缺乏组最高（P < 0.05），其中VitD不足组的DC、RMSSD和LF低于充足组，AC值高于充足组（P < 0.05）；VitD缺乏组的RR间期总体标准差（SDNN）、高频功率（HF）低于VitD充足组（P < 0.05）。VitD缺乏组的VitD水平与DC、SDNN、SDANN、RMSSD、LF、HF呈正相关（P < 0.05），与AC呈负相关（P < 0.05）；VitD不足组的VitD水平与AC呈负相关（r=-0.257，P < 0.05）。结论 VitD不足和缺乏的学龄前期肥胖儿童均存在心脏自主神经功能障碍，且VitD浓度越低，心脏迷走神经张力越弱。

Objective To study the effect of vitamin D (VitD) deficiency on cardiac autonomic nerve function in obese pre-school children. Methods A total of 242 pre-school children with simple obesity were enrolled, and according to the serum 25-(OH) VitD level, they were divided into VitD deficiency group (76 children), VitD insufficiency group (83 children), and VitD sufficiency group (83 children). The three groups were compared in terms of deceleration capacity (DC) of heart rate, acceleration capacity (AC) of heart rate, and heart rate variability (HRV). The correlations of VitD level with DC, AC, and HRV were analyzed for the VitD insufficiency and VitD deficiency groups. Results The VitD deficiency group had the lowest DC, root mean square of successive differences between adjacent RR intervals (RMSSD), and low-frequency power (LF) and the highest AC (P < 0.05). The VitD insufficiency group had significantly lower DC, RMSSD, and LF and significantly higher AC compared with the VitD sufficiency group (P < 0.05). The VitD deficiency group had significantly lower standard deviation of normal-to-normal RR intervals (SDNN) and high-frequency power (HF) than the VitD sufficiency group (P < 0.05). In the VitD deficiency group, VitD level was positively correlated with DC, SDNN, standard deviation of average normal-to-normal RR intervals, RMSSD, LF, and HF and was negatively correlated with AC (P < 0.05). In the VitD insufficiency group, VitD level was negatively correlated with AC (P < 0.05). Conclusions Obese pre-school children with VitD insufficiency or deficiency have cardiac autonomic dysfunction, and cardiac vagal tone decreases with the reduction in VitD level.