Low-level Pb and cardiovascular responses to acute stress in children: the role of cardiac autonomic regulation.

OBJECTIVE: A number of studies suggest that Pb exposure increases cardiovascular disease risk in humans. As a potential mechanism for this effect, we recently reported a significant association between early childhood Pb levels and cardiovascular response to acute stress. The current study considers the association between current Pb levels and the autonomic nervous system activation pattern underlying the cardiovascular response to stress in a new cohort of children.
METHODS: We assessed blood Pb levels as well as cardiovascular responses to acute stress in 9-11 year old children (N=140). Sympathetic activation (measured with pre-ejection period) and parasympathetic activation (measured with high frequency heart rate variability) were also assessed.
RESULTS: In a sample with very low levels of blood Pb (M=1.0 μg/dL), we found that increasing blood Pb was associated with coinhibition of sympathetic and parasympathetic activation in response to acute stress. In addition, increasing Pb levels were associated with the hemodynamic stress response pattern typical of coinhibition--significantly greater vascular resistance and reduced stroke volume and cardiac output.
CONCLUSIONS: Blood Pb levels were associated with significant autonomic and cardiovascular dysregulation in response to acute psychological stress in children. Moreover, these effects were significant at Pb levels considered to be very low and notably well below the 10 μg/dL, the Centers for Disease Control and Prevention definition of an elevated blood Pb level. The potential for autonomic dysregulation at levels of Pb typical for many US children would suggest potentially broad public health ramifications.