Abstract
The aim of this study was to assess the value of the children’s version of the Rey-Osterrieth Complex Figure Test as a screening test in a population exposed to different mixtures of neurotoxicants. Copy and Immediate Recall scores were evaluated through the test. Children were recruited from three sites; an area with natural contamination by fluoride and arsenic (F-As), a mining-metallurgical area with lead and arsenic contamination (Pb-As) and a malaria zone with the evidence of fish contaminated with dichlorodiphenyltrichloroethane (DDT) and polychlorinated biphenyls (PCBs). Children aged 6-11 years old, living in one of the three polluted sites since birth were recruited (n=166). The exposure was evaluated as follows: fluoride and arsenic in urine, lead in blood and DDT, dichlorodiphenyldichloroethylene (DDE) and PCBs in serum. To evaluate the test performance, z-scores for Copy and Immediate Recall were calculated. The proportion of children by residence area with performance lower than expected by age (below -1 SD) for Copy and Immediate Recall was in the F-As area (88.7% and 59%) and in the DDT-PCBs area (73% and 43.8%), respectively. In the Pb-As area, the proportion was 62% for both tests. After adjustment, Copy correlated inversely with fluoride in urine (r=-0.29; p<0.001) and Immediate Recall correlated inversely with fluoride in urine (r=-0.27; p<0.05), lead in blood (r=-0.72; p<0.01), arsenic in urine (r=-0.63; p<0.05) and DDE (r=-0.25; p<0.05). This study provided evidence that children included in this research are living in high risk areas and were exposed to neurotoxicants. Poor performance in the test could be explained in some way by F, Pb, As or DDE exposure, however social factors or the low quality of school education prevalent in the areas could be playing an important role.
Excerpt
4. Discussion
This study provides evidence that children living in high risk
areas were exposed to either F, As, Pb, DDT or PCBs and these
contaminants could contribute, to some degree, to children’s low
performance observed in the tests of the Rey-Osterrieth Complex
Figure. The highest proportion of children (89%) with Copy
performance below 1 SD was observed in children from F–As
area. Approximately 9 out of 10 children were unable to copy the
ROCF as expected for their age. For example, the expected score on
Copy for a 6-year-old child is 9.94 2.28 points. A child classified in
the category below 1 SD means that his score was lower than 7.66.
In the F–As area children had z-scores as low as 5 SD (scoring only
two points on the test). For Immediate Recall, the proportion of
children in the lowest category was 59% and almost 6 out of 10
children were unable to draw the figure as expected for their age after
3 min had elapsed. Following the same example of a 6-year-old child,
the expected value for drawing the figure from memory is
7.26 2.45. One child classified in the 1 SD category had a score
below 4.81 points. Fluoride correlated inversely with Copy and
Immediate Recall r = 0.29 and r = 0.27 (adjusted values). In the F–
As area, the mean of FU was 5.6 1.7 and the proportion of children
with FU levels over 2 mg/gcrt was 97.5%. All children had some degree
of dental fluorosis as an indicator of chronic exposure to fluoride. In
the Pb–As and DDT–PCBs, none of the children had dental fluorosis
(data not shown). Previous data have reported a similar association
between Copy scores and FU in children (r = 0.27; p < 0.05) at mean
values of 4.3 1.5 mg/gcrt (Caldero´n et al., 2001b). We have reported
previous studies with similar data. For example, in children exposed
to F via drinking water (with FU levels above 5 mg/gcrt) we observed
an inverse association with Performance IQ scores (b = 13,
p < 0.001) (Rocha-Amador et al., 2007). Other epidemiological and
experimental data support the potential of F to damage the Central
Nervous System (CNS). For example, Full IQ score reductions were
found in children exposed to F in water above 2.0 mg/L (Li et al., 1995;
Lu et al., 2000; Zhao et al., 1996; Xiang et al., 2003). In experimental
animal studies, alterations in nicotinic acetylcholine receptors, brain
membrane lipids and oxidative stress after fluoride exposure have
been reported (Mullenix et al., 1995; Shivarajashankara et al.,
2002a,b; Long et al., 2002; Guan et al., 1998).
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