title: Factors affecting hand tremor and postural sway in children.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  Hand tremor and postural sway, as well as hair mercury concentrations, were measured in 155 boys and 148 girls at age 7 years.
  
  
  RESULTS
  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).
  
  
  CONCLUSIONS
  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.
authors: Department of Environmental Health Sciences, Akita University School of Medicine, 1-1-1 Hondo, 010-8543, Akita, Japan.
authors: Toyoto
authors: T
authors: Iwata
authors: Kunihiko
authors: K
authors: Nakai
authors: Mineshi
authors: M
authors: Sakamoto
authors: Miwako
authors: M
authors: Dakeishi
authors: Hiroshi
authors: H
authors: Satoh
authors: Katsuyuki
authors: K
authors: Murata