While the study examined 5 to 11 year olds with asthma, the findings most likely could be extrapolated to include children without asthma who "act out" or experience depression and anxiety, according to Kimberly Yolton, Ph.D., a researcher at the Children's Environmental Health Center at Cincinnati Children's and the study's main author
The study will be presented at 8:30 a.m. Pacific time Sunday, April 30, at the annual meeting of the Pediatric Academic Societies in San Francisco.
"This study provides further incentive for states to set public health standards to protect children from exposure to environmental tobacco smoke," says Dr. Yolton.
Dr. Yolton examined 225 children and pre-teens exposed to at least five cigarettes a day. On average, the children were exposed to approximately 14 cigarettes a day. The children were enrolled in an asthma intervention study. Dr. Yolton included additional measures to assess child behaviors.
To measure exposure to environmental tobacco smoke, Dr. Yolton measured levels of cotinine in the children's blood. Cotinine is a substance produced when nicotine is broken down by the body and can be measured in blood, urine, saliva and hair. It is considered the best available marker of environmental tobacco smoke exposure.
Dr. Yolton found a relationship between cotinine levels and increases in acting out; increases in holding things in, often manifested by anxiety and depression; increases in behavior problems as rated by parents, and behavior and school problems as rated by teachers; and, decreases in the ability to adapt to behavior problems.
"The greater the exposure to tobacco smoke, the greater the problems these children had," says Dr. Yolton. "Behavior problems in c hildren have increased from 7 to 18 percent 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."
In the United States, about 25 percent of children are exposed to environmental tobacco smoke in their own homes, yet more than 50 percent of children have detectable levels of cotinine in their blood, according to Dr. Yolton.
Previous studies have found link between tobacco smoke and birth weight, number of infections and other health problems, including asthma exacerbations. In a groundbreaking study in 2002, Dr. Yolton found that exposure to environmental tobacco smoke, even at extremely low levels, is associated with decreases in certain cognitive skills, including reading, math, and logic and reasoning, in children and adolescents.