Home Original News Half a million cases of children with ADHD linked to lead exposure and environmental tobacco smoke
Half a million cases of children with ADHD linked to lead exposure and environmental tobacco smoke PDF Print E-mail
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Written by Roman Bystrianyk   
Saturday, 24 March 2007 00:00

Attention deficit hyperactivity disorder, or ADHD, is one of the most common childhood disorders. The Centers for Disease Control (CDC) estimates that 4.4 million children between the ages 4-17 have been diagnosed with ADHD by a healthcare professional, and as of 2003, 2.5 million children ages 4-17 are currently receiving medication for the disorder. In 2003, 7.8% of school-aged children were reported to have an ADHD diagnosis by their parents. 

A large number of studies have found an association between prenatal environmental tobacco smoke (ETS) exposure and ADHD. In case controlled studies, researchers have found a 2 to 4-fold increased risk of ADHD associated with prenatal ETS exposure. 

Lead is a heavy metal that serves no purpose in the body and can result in toxic effects. The nervous system is the most sensitive to lead exposure. Fetuses and young children are particularly vulnerable to neurologic damage from lead exposure because their brains are still developing and their brain-blood barrier is incomplete. According to the CDC, “There may be no lower threshold for some of the adverse neurologic effects of lead in children; some of these effects have been documented at exposure levels once thought to cause no harmful effects.” 

Children can suffer neurologic effects at low levels of lead exposure. There is a large body of evidence that links a decrease in IQ and other neuropsychologic defects with lead exposure. Numerous studies have found an association between lead levels measured in the blood or teeth to higher rates of inattention and impulsivity.

A recent study in Environmental Health Perspectives, examined the relationship between ETS and environmental lead with ADHD. The authors examined over 4,700 children for this study for ADHD, exposure to cigarette smoke during pregnancy, and child blood lead concentrations. 

The study authors found that 8.2% had parent reported ADHD with 4.3% reporting stimulant medication usage. This percentage is equivalent to 3.8 million children with parent reported ADHD and 2 million children on medication. 

After analysis the authors found a significant link in children that were exposed to prenatal ETS or had elevated blood lead concentrations to ADHD. “Our estimates indicate that 32.2% of ADHD cases among children 4-15 years of age were attributable to having either prenatal ETS exposure or blood lead > 2.0 μg/dL, which corresponds to 480,000 excess cases of ADHD among U.S. children 4-15 years of age.” 

The overall adjusted risk for ADHD was 2.5-fold higher for children prenatally exposed to ETS. Also, children whose blood lead level was > 2.0 μg/dL were at a 4.1-fold increased risk of ADHD. 

The authors conclude, “This study confirms the previously observed association of prenatal ETS exposure and ADHD. We also found a significant dose-response relationship between childhood lead exposure and ADHD. This analysis indicates that 270,000 ADHD cases in children 4-15 years of age are attributable to prenatal ETS exposure, and 290,000 cases of ADHD among U.S. children 4-15 years of age are attributable to environmental lead exposure. The findings of this study underscore the profound behavioral health impact of these prevalent exposures, and highlight the need to strengthen public health efforts to reduce prenatal ETS exposure and childhood lead exposure.”

Source: Environmental Health Perspectives, December 2006


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