Exposure to Both Lead and Prenatal Tobacco Smoke Raise Risk of ADHD in Children and Teens

Monday, October 20, 2008

A new study from Cincinnati Children’s Hospital Medical Center finds that children in the United States who are exposed prenatally to tobacco smoke and during childhood to environmental lead face a particularly high risk for ADHD.

The study will be presented on Monday Oct. 20 at the annual meeting of the Society for Developmental and Behavioral Pediatrics in Cincinnati.
“Tobacco and lead exposure together seem to have a synergistic, negative effect,” says Tanya Froehlich, MD, a physician in the Division of Developmental and Behavioral Pediatrics at Cincinnati Children’s and the study’s lead author. “Our study estimates that 35 percent of ADHD in children between the ages of 8 and 15 could be reduced by eliminating both environmental exposures. This equates to more than 800,000 of the 2.4 million children in this age group across the United States estimated to have ADHD. Although we tend to focus on ADHD treatment rather than prevention, our study suggests that reducing exposures to environmental toxicants might be a key way to lower rates of ADHD.”

The Cincinnati Children’s researchers found that children exposed prenatally to tobacco smoke had a 2.4 fold increased odds of ADHD. Those with blood lead levels in the top third -- despite largely having levels well below the Centers for Disease Control action level of 10 micrograms per deciliter -- had a 2.3 fold increased odds of ADHD. Multiplying the risks due to the individual toxicants would give a 5.5 fold increased odds, yet Dr. Froehlich and her colleagues found the risk of ADHD 8.1 times higher for children exposed to both tobacco and lead compared to unexposed children.

“If children are exposed to both lead and prenatal tobacco, it’s not like being exposed individually, it’s considerably worse,” says Dr. Froehlich.

The study is based on data on 8 to 15 years olds gathered between 2001 and 2004 from a validated national database, the National Health and Nutrition Examination Survey (NHANES) from the National Center for Health Statistics at the Centers for Disease Control and Prevention. NHANES is a nationally representative sample of the United State population, designed to collect information about the health and diet of people in the U.S.

Prenatal tobacco exposure was measured by maternal report of cigarette use during pregnancy. Lead exposure was assessed using current blood lead level. The presence of ADHD was based on the Diagnostic and Statistical Manual for Mental Disorders, Fourth Edition, considered to be the “gold standard” for defining specific mental health conditions.

“These findings highlight the need to strengthen public health efforts to reduce prenatal tobacco smoke exposure and exposure to lead during childhood,” says Dr. Froehlich.

Cincinnati Children's is one of America’s top three children’s hospitals for general pediatrics and is highly ranked for its expertise in digestive diseases, respiratory diseases, cancer, neonatal care, heart care and neurosurgery, according to the annual ranking of best children's hospitals by U.S. News & World Report. One of the three largest children’s hospitals in the U.S., Cincinnati Children’s is affiliated with the University of Cincinnati College of Medicine and is one of the top two recipients of pediatric research grants from the National Institutes of Health.

For its achievements in transforming healthcare, Cincinnati Children's is one of six U.S. hospitals since 2002 to be awarded the American Hospital Association-McKesson Quest for Quality Prize® for leadership and innovation in quality, safety and commitment to patient care. The hospital is a national and international referral center for complex cases, so that children with the most difficult-to-treat diseases and conditions receive the most advanced care leading to better outcomes.