Department of Environmental Health Sciences, Akita University School of Medicine, 1-1-1 Hondo, 010-8543, Akita, Japan.
Environ Health Prev Med. 2006 Jan;11(1):17-23. doi: 10.1007/BF02898203.
It is crucial to consider covariates relevant for outcome variables in developing dose-effect relations of environmental hazardous toxins. The aim of this study was to clarify the covariates affecting hand tremor and postural sway in children.
Hand tremor and postural sway, as well as hair mercury concentrations, were measured in 155 boys and 148 girls at age 7 years.
Current mercury concentrations in child hair ranged from 0.35 to 6.32 μg/g (geometric mean, 1.71 μg/g for boys and 1.58 μg/g for girls), and were not significantly correlated with the neuromotor parameters. All hand tremor and postural sway parameters, except for tremor intensity at 1-6 Hz with non-dominant hand, were significantly larger in the boys than in the girls. Using multiple regression analysis, some postural sway parameters were related negatively to age in the boys and girls (p<0.05), and positively to height (p<0.05). Similarly, hand tremor parameters were positively related to age, height and heart rate either in the boys or in the girls (p<0.05). Also, there were positive relationships between tremor intensity at 1-6 Hz and transversal and sagittal sways at 1-2 Hz and 2-4 Hz (p<0.05).
Heart rate and postural sway, together with age, sex, and height, should be considered in interpreting hand tremor in children. Hand tremor or postural sway may not be so sensitive or specific to methylmercury exposures at levels of less than 7 μg/g in hair.
在建立环境有害毒素的剂量-效应关系时，考虑与结局变量相关的协变量至关重要。本研究旨在阐明影响儿童手部震颤和姿势摆动的协变量。
在 7 岁时，测量了 155 名男孩和 148 名女孩的手部震颤和姿势摆动以及头发中的汞浓度。
儿童头发中的当前汞浓度范围为 0.35 至 6.32μg/g（男孩几何均值为 1.71μg/g，女孩为 1.58μg/g），与神经运动参数无显著相关性。除非优势手 1-6Hz 的震颤强度外，所有手部震颤和姿势摆动参数在男孩中均显著大于女孩。使用多元回归分析，一些姿势摆动参数在男孩和女孩中与年龄呈负相关（p<0.05），与身高呈正相关（p<0.05）。同样，手部震颤参数与年龄、身高和心率呈正相关，无论是在男孩还是女孩中（p<0.05）。此外，1-6Hz 的震颤强度与 1-2Hz 和 2-4Hz 的横向和纵向摆动之间存在正相关关系（p<0.05）。
在解释儿童手部震颤时，应考虑心率和姿势摆动以及年龄、性别和身高。在头发中汞含量低于 7μg/g 的情况下，手部震颤或姿势摆动可能对甲基汞暴露的敏感性或特异性不高。
