Re-post - abstracts on chelation, lead, and IQ

[Guest guest]

Repost w/ comments from Cheryl-

The first abstract is the one I mentioned. Evidently

they did a follow-up which is of even more concern.

From what the second abstract says, by six

months, the lead levels had fallen by similar levels

in both the chelated and non-chelated children. Only

the NON-chelated children had cognitive gains of 4.0

points per 10 microg/dL fall in blood lead levels.

There was an improvement of scores ONLY in the placebo

group.

Cheryl

N Engl J Med 2001 May 10;344(19):1421-6 Related

Articles, Links

Comment in:

N Engl J Med. 2001 May 10;344(19):1470-1.

N Engl J Med. 2001 Oct 18;345(16):1212-3.

The effect of chelation therapy with succimer on

neuropsychological development in children exposed to

lead.

Rogan WJ, Dietrich KN, Ware JH, Dockery DW, Salganik

M, Radcliffe J, RL, Ragan NB, Chisolm JJ Jr,

Rhoads GG; Treatment of Lead-Exposed Children

Trial Group.

National Institute of Environmental Health Sciences,

Research Triangle Park, NC 27709, USA.

rogan@...

BACKGROUND: Thousands of children, especially poor

children living in deteriorated urban housing, are

exposed to enough lead to produce cognitive

impairment. It is not known whether treatment to

reduce blood lead levels prevents or reduces such

impairment. METHODS: We enrolled 780 children with

blood lead levels of 20 to 44 microg per deciliter

(1.0 to 2.1 micromol per liter) in a randomized,

placebo-controlled, double-blind trial of up to

three 26-day courses of treatment with succimer, a

lead chelator that is administered orally. The

children lived in deteriorating inner-city housing

and were 12 to 33 months of age at enrollment; 77

percent were black, and 5 percent were Hispanic.

Follow-up included tests of cognitive, motor,

behavioral, and neuropsychological function over a

period of 36 months.

RESULTS: During the first six months of the trial, the

mean blood lead level in the children given succimer

was 4.5 microg per deciliter (0.2 micromol

per liter) lower than the mean level in the children

given placebo (95 percent confidence interval, 3.7 to

5.3 microg per deciliter [0.2 to 0.3 micromol per

liter]).

At 36 months of follow-up, the mean IQ score of

children given succimer was 1 point lower than that of

children given placebo, and the behavior of

children given succimer was slightly worse as rated by

a parent.

However, the children given succimer scored slightly

better on the Developmental Neuropsychological

Assessment, a battery of tests designed to

measure neuropsychological deficits thought to

interfere with learning. All these differences were

small, and none were statistically significant.

CONCLUSIONS: Treatment with succimer lowered blood

lead levels but did not improve scores on tests of

cognition, behavior, or neuropsychological

function in children with blood lead levels below 45

microg per deciliter. Since succimer is as effective

as any lead chelator currently available, chelation

therapy is not indicated for children with these blood

lead

levels.

Publication Types:

Clinical Trial

Multicenter Study

Randomized Controlled Trial

PMID: 11346806 [PubMed - indexed for MEDLINE]

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Pediatrics 2002 Oct;110(4):787-91 Related Articles,

Links

Do children with falling blood lead levels have

improved cognition?

Liu X, Dietrich KN, Radcliffe J, Ragan NB, Rhoads GG,

Rogan WJ.

Epidemiology Branch, National Institute of

Environmental Health Sciences, Research Triangle Park,

North Carolina 27709, USA.

OBJECTIVE: Exposure to lead at levels encountered by

urban children impairs cognitive development. An

observational study suggested improvement in IQ

when blood lead level fell, but the only randomized

trial of chelation showed no benefit in IQ.

METHODS: We did a new analysis of the data from the

clinical trial using change in blood lead level as the

independent variable. The 741 children

began with blood lead levels between 20 and 44

microg/dL, and were 13 to 33 months old at

randomization to chelation or placebo.

Blood lead levels were measured repeatedly, and

cognitive tests were given at baseline, 6 months, and

36 months follow-up.

RESULTS: By 6 months after randomization, blood lead

levels had fallen by similar amounts in both chelated

and placebo children, despite the immediate

drops in the chelated group; there was no association

between change in blood lead level and change in

cognitive test score. Blood lead levels continued to

fall.

At 36 months follow-up, in the *placebo group only*,

cognitive test scores had *increased* 4.0 points per

10 microg/dL fall in blood lead level from

baseline to 36 months follow-up and 5.1 points from 6

to 36 months.

CONCLUSIONS: The improvement in scores in the placebo

group only implies that factors other than declining

blood lead levels per se are responsible

for cognitive improvement; it is possible but less

likely that succimer, the active drug, impairs

cognition.

Publication Types:

Clinical Trial

Randomized Controlled Trial

PMID: 12359796 [PubMed - indexed for MEDLINE]

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