A first-of-its-kind national study has found that pre-birth exposure to cigarette smoke and high levels of lead in children can be linked to higher rates of attention deficit/hyperactivity disorder (ADHD) in youth.
Children with ADHD typically have trouble concentrating, experience difficulty controlling their impulses, find it hard to play quietly and often seem to fidget or squirm excessively. The disorder among youths has serious implications in the classroom and on the playground and, for adults, can lead to an inability to perform well at the workplace.
Other smaller studies have examined the effects of lead and prenatal smoke to ADHD. However, this study is unique because it relied, in part, on data from the National Health and Nutrition Examination Survey, a national survey of the U.S. population. After parents or caregivers completed the survey, they filled out another interview form that was used to gather information on ADHD symptoms. To determine if children were exposed to prenatal tobacco smoke, caregivers were asked if the child’s biological mother smoked at any time during pregnancy. To determine the levels of lead in children, the researchers used current blood lead concentrations.
The researchers found that about 8.7 percent of 8- to 15-year-old survey participants met the criteria for having ADHD, which is equivalent to about 2.4 million children in the United States. Children who were exposed to prenatal cigarette smoke were more than twice as likely to meet the criteria for having ADHD, compared to children who were not exposed to smoke in the womb. Children with high lead levels also were at significantly higher risks of having ADHD than those with moderate and low lead levels.
Children who were exposed to both prenatal smoke and registered high lead levels had a greater than eightfold increased in the likelihood of having ADHD. This finding suggested that the combination of prenatal smoke and lead exposure created a joint effect that was greater than if the independent effects were multiplied.
Though the United States has made strong headway in reducing prenatal exposure to some toxicants, such as alcohol, the report’s authors noted that 15 percent of women in a 2004 U.S. population-based study reported smoking during pregnancy. Also, an estimated 1.6 percent of U.S. children had blood lead levels above the level of concern of the Centers for Disease Control and Prevention. The report’s findings suggest that reducing prenatal smoke exposure and childhood lead exposure could be an important way to prevent ADHD in children.