EMBARGOED UNTIL
12:01 AM EDT/Friday, April 17, 2009
Contact: Donna Krupa
Newsroom: (504) 670-4525 or 4526
Office: (301) 634-7209
Cell: (703) 967-2751
dkrupa@the-aps.org
Low Lead Levels In Children
Can Affect Cardiovascular Responses To Stress
NEW ORLEANS—Even low levels
of lead found in the blood during early childhood can adversely affect how
the child’s cardiovascular system responds to stress and could possibly lead
to hypertension later in life, according to a study from the State
University of New York (SUNY) at Oswego.
Lead exposure was associated with an increase in
vascular resistance when the children worked on a stressful computer task.
Vascular resistance is a measure of tension within the blood vessels.
Increased vascular resistance may lead to hypertension if it continues over
time.
The study also found that lead exposure was associated
with a decrease in circulating aldosterone levels. Aldosterone is a hormone
that helps regulate blood pressure.
The study, Lead exposure
and cardiovascular dysregulation in children, was conducted by
James A. MacKenzie, Brooks B. Gump, Kristen Roosa, Kestas Bendinskas
and Amy Dumas of the State University of New York, Oswego; Robert Morgan of
Oswego Family Physicians; and Patrick Parsons of the New York State
Department of Health. The researchers will present their findings during the
122nd annual meeting of The American Physiological Society (www.the-aps.org/press).
The meeting is part of the Experimental Biology 2009 conference, to
take place April 18-22 in New Orleans.
Ongoing research
In an earlier study with a different group of children,
the researchers found that higher lead levels measured at 2 years of age
were associated with an increased vascular response to stress later in life
(average of 9.5 years of age). The present study aimed to determine whether
this association was true when both lead and vascular responses were
measured simultaneously, and if it did, how this happens.
The researchers gave 140 children, 9-11 years old, a
psychologically stressful computer task. They measured the children’s
cardiovascular function, including total peripheral resistance, while they
were at rest and while they performed the stressful task. Total peripheral
resistance is a measure of arterial pressure relative to cardiac output.
The researchers compared the current blood lead levels
of the children to their cardiovascular functioning during the experiment.
As with the earlier study, they found that lead levels did correlate to the
children’s total peripheral resistance response to the stressful task. The
finding is important because increases in total peripheral resistance may
predispose people to hypertension later in life.
Low lead levels
One of the study’s most important findings is that all
of the participants had very low lead levels, well below the 10 micrograms
per deciliter that the CDC defines as a level of concern. The highest lead
level for the children in this study was 3.8 micrograms per deciliter.
“The interesting thing was that the levels of lead were
all pretty low in the children who participated,” Dr. MacKenzie said. “We’re
seeing the negative effects at these low levels.” While these are
preliminary findings, the issue deserves more study, he said.
Children may be exposed to lead-based paint or
lead-contaminated dust in their homes or pick it up from the soil outside.
The Centers for Disease Control and Prevention (CDC) has pushed to minimize
or eliminate all childhood exposure to lead.
Search for the ‘how’
In trying to find an explanation for how lead affects
total peripheral resistance, the researchers found increased sympathetic
nervous system activity during rest and, paradoxically, a depressed
sympathetic response during the stressful computer task. Activation of the
sympathetic nervous system produces the “fight or flight” response, raising
the heart rate and constricting the blood vessels, among other things.
Sympathetic nervous system activity is an appropriate response to stress,
but can be harmful if activated for a long time.
“We believe lead causes an increase in sympathetic
nervous activity during rest which reduces the body’s ability to generate a
response when stress comes along,” Dr. MacKenzie said. In essence, the
cardiovascular system is revving all the time, making it harder for the body
to increase in sympathetic nervous system activity when needed.
The study also found that serum aldosterone levels go
down with higher lead levels, making it harder for the body to activate the
sympathetic nervous system when needed. Dr. MacKenzie cautioned that the
data on aldosterone and sympathetic activity is still preliminary and may be
a focus of future research.
********
Physiology
is the study of how molecules, cells, tissues and organs function to create
health or disease. The American Physiological Society (APS) has been an
integral part of this scientific discovery process since it was established
in 1887.
Editor’s
Notes: To arrange an interview with Dr. MacKenzie, please contact Donna
Krupa at
dkrupa@the-aps.org (301) 634-7209 before April 17 and at 504.670.4525 or
504.670.4526 April 17-15.
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