HONOLULU -- More than 800,000 cases of attention-deficit/hyperactivity disorder in the United States may be linked to childhood exposure to lead and intrauterine exposure to tobacco smoke, Dr. Tanya E. Froehlich said at the joint meeting of the Pediatric Academic Societies and the Asian Society

Her cross-sectional study used data from a nationally representative sample of children aged 8-15 years, which was part of the National Health and Nutrition Examination Survey (NHANES) conducted between 2001 and 2004. Data were collected from 2,588 children and their parents.

Dr. Froehlich of Cincinnati Children's Hospital Medical Center was able to determine that 9% of that sample met DSM-IV criteria for ADHD.

In the bivariate analysis, blood lead levels, in utero tobacco smoke, and serum cotinine were all significantly associated with ADHD. However, after controlling for current tobacco exposure, age, sex, race/ethnicity, preschool attendance, maternal age at child's birth, and birth weight in a multivariate analysis, only lead and in utero tobacco smoke remained significantly associated with ADHD.

Children whose mothers reported smoking during pregnancy were 2.4-fold more likely to develop ADHD than were those whose mothers reported not smoking during pregnancy. Compared with children in the first tertile of blood lead level, those in the second tertile were 1.7-fold more likely to develop ADHD. That increased to 2.3-fold for children in the third tertile. All of those results were statistically significant.

Dr. Froehlich was able to determine that 35% of the current prevalent cases of ADHD in the United States could be linked to in utero tobacco exposure or to blood lead levels in the third tertile. This corresponds to 824,000 excess cases of ADHD.

Dr. Froehlich stated that she had no conflicts of interest related to her presentation.