Asthmatic children who are exposed to second-hand smoke have significant increases in problem behaviors at home and at school, according to research reported at the Pediatric Academic Societies meeting here.
Although the study was limited to elementary school-age children with asthma, the results are likely to apply to kids without asthma as well, said Kimberly Yolton, Ph.D., an investigator at Cincinnati Children's Hospital Medical Center.
"This study provides further incentive for states to set public health standards to protect children from exposure to environmental tobacco smoke," Dr. Yolton said.
She and colleagues evaluated at 225 children between the ages of five and 12 who were enrolled in an asthma intervention trial. All children were exposed to second-hand smoke from five or more cigarettes per day.
The investigators assessed levels of exposure to environmental tobacco smoke through parental reports and through evaluation of the metabolite cotinine in children's serum and hair.
Parents and teachers also reported behavioral problems using a validated instrument, the Behavioral Assessment System for Children.
The mean age of the children in the study was 8.6 and 62% were male. The children were exposed to smoke from 14.2 cigarettes daily on average.
The authors found that according to parental ratings, there was a significant association between serum cotinine levels and increases in externalizing, or acting out; internalizing or being overcontrolled, and behavior symptoms.
There were also significant associations between cotinine levels and teacher ratings for behavior symptoms, and an inverse relationship between cotinine levels and adaptive behaviors.
"The greater the exposure to tobacco smoke, the greater the problems these children had," Dr. Yolton said. "Behavior problems in children have increased from 7% to 18% over the last 20 years for reasons that are poorly understood. Exposure to environmental tobacco smoke is increasingly recognized as a risk factor for child behavior problems."
She said that about one in four American children are exposed to environmental tobacco smoke at home, yet more than half of all children have detectable serum cotinine levels.
In a study published in the Environmental Health Perspectives in January 2005, Dr. Yolton and colleagues reported that exposure to even low levels of environmental tobacco smoke is associated with decreases in cognitive skills essential for reading, math, logic and reasoning in children and adolescents.
When the researchers in that study adjusted their calculations for sex, race, region, poverty, parent education and marital status, ferritin, and blood lead concentration, they found that exposure to secondhand smoke remained an independent significant predictor of decreased scores on reading, math, and block design.
They also found that as cotinine levels increased, test scores decreased, and children with cotinine values of more than 3 ng/mL had test scores that averaged 4.8 points lower (out of 100) than those with cotinine concentrations of less than 0.1 ng/mL.
- Reviewed by Robert Jasmer, MD Assistant Professor of Medicine, University of California, San Francisco
Pediatric Academic Societies Annual MeetingSource Reference: Yolton K et al. "Environmental Tobacco Smoke and Child Behaviors." Abstract 3135.3, presented April 30, 2006.