Environmental lead and children's intelligence

doi:10.1136/bmj.310.6991.1408a

From trainee to consultant, BMJ Group offers doctors around the world tailored information, special events, learning resources and recruitment services at every step along their career path.

... by doctors, for doctors, for patients
We are open for entries!

Online learning

BMJ Learning

High-quality CME / CPD for doctors and other healthcare professionals. BMJ Learning features hundreds of accredited, peer-reviewed learning modules in text, video, and audio formats. Find out more

Courses and Qualifications

BMJ Masterclasses

BMJ Masterclasses, led by experts, help clinicians to use the latest evidence and recent guidelines in practice and meet their CPD/CME requirements. Find out more

Exam Preparation

The leading provider of online exam preparation, helping over 167,000 healthcare professionals to pass their exams. Find out more

onExamination

Search all BMJ comment articles:

From

Limit by

Access to the full text of this article requires a subscription or payment. Please log in or subscribe below.

Studies included in the meta-analysis are not representative

Herbert L Needleman

Professor of psychiatry and paediatrics Western Psychiatric Institute and Clinic, University of Pittsburgh Medical Center, Pittsburgh, PA 15213-2593, USA

EDITOR,—Stuart J Pocock and colleagues' metanalysis of 26 studies of asymptomatic exposure to lead in children concludes that “the evidence strongly supports an inverse association between body lead burden and child IQ.”1 The authors then urge caution before the relation is accepted as causal. They do this on the basis of the following considerations: Are the studies representative? Is confounding adequately dealt with? Is selection bias at work? Is causality reversed: does low IQ cause ingestion of lead?

These questions have been asked and answered before. The criticism of non-representativeness could readily be applied to Pocock andcolleagues' analysis, which includes …