Elevated blood lead concentrations associated with behavioral problems in children

1. The mean blood lead concentration in a Chinese pre-school cohort was 6.4 µg/dL. 

2. Detriment in emotional reactivity, anxiety, and pervasive developmental were noted even with a 1 µg/dL increase in blood lead concentration.  

Evidence Rating Level: 3 (Average)        

Study Rundown: The effects of lead poisoning seem to be dependent on the level of exposure and the age at which the exposure occurs.  Children younger than the age of 6 are especially susceptible due to an incomplete blood-brain barrier.  While increased blood lead levels have been well correlated with lower IQ levels in children, the effects on behavior are not as well characterized. In this study, the researchers examined the relationship between blood lead concentrations (BLC) and behavioral problems in a Chinese per-school cohort.

The authors found that elevated blood lead concentrations were associated increased behavioral problems, internalizing and developmental problems in this cohort.  Interestingly, this association appeared to be stronger in girls.  Limitations of the study include the fact that blood lead levels were measured once, between the ages of 3-5 years, and behavioral assessment was not performed until at age 6. Moreover, behavioral changes were measured by parents and teachers, rather than medically trained professionals.  Therefore, the scores calculated by parents and teachers were quite variable.

Click to read the study in JAMA Pediatrics

Relevant Reading: Pre- and postnatal lead exposure and behavior problems in school-aged children

In-Depth [prospective cohort]: Data for this study was obtained from the China Jintan Child Cohort Study, which included children aged 3 to 5 years of age from four preschools.  This study used a sample of 1341 children with blood lead data that was available.  BLC were tested once for each child while between the ages of 3-5.  Parents completed Chinese versions of the Child Behavior Checklist (CBCL), and teachers completed the Caregiver-Teacher Report Form (C-TRF). Child and family characteristics such as residence, parental education level, father’s occupation, and marital status of the parents were controlled for.

The mean blood lead concentration was 6.4 µg/dL and was higher in boys and increased with age at the time of the blood test.  A 1 µg/dL increase in BLC resulted in a 0.322 (95%CI, 0.058-0.587) increase in emotional reactivity, 0.253 (95%CI, 0.016-0.500) increase in anxiety problems, and a 0.303 (95%CI, 0.046-0.560) increase in pervasive developmental problems.  All of these were teacher-reported scores.  This was true especially for girls.  Parent reported behavioral scales were not significantly associated with blood lead levels.

Image: PD

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