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Childhood Tobacco Smoke Exposure Ups Risk of ADHD

Hispanics and other races at higher risk than non-Hispanic whites and blacks

MONDAY, Sept. 20 (HealthDay News) -- Exposure to environmental tobacco smoke in childhood increases the odds of attention-deficit/hyperactivity disorder (ADHD), but the magnitude of risk seen with elevated serum cotinine levels varies by race, according to research published online Sept. 20 in Pediatrics.

Xiaohui Xu, Ph.D., of the University of Florida in Gainesville, and colleagues examined the association between postnatal environmental tobacco smoke exposure, measured with serum cotinine levels, and ADHD among children 4 to 15 years of age. After controlling for prenatal exposure, the interactions of race and serum cotinine levels with ADHD were also studied.

Overall, the researchers found that ADHD prevalence increased as serum cotinine levels increased, but the magnitude of the cotinine effect varied by race. Comparing same-race children with the highest and lowest cotinine levels showed an ADHD odds ratio of 2.72 for Mexican-American children and 5.32 for children of races designated as "other." For non-Hispanic whites and non-Hispanic blacks, there were no significant associations between cotinine level and ADHD.

"Although it is impossible to control for all confounders and/or biases in measurements of outcome and covariates in our analysis, this study supports the hypothesis that postnatal environmental tobacco smoke exposure, independent of prenatal smoking exposure, is an important risk factor for ADHD. Moreover, our study suggests that the effects of postnatal environmental tobacco smoke exposure on ADHD may differ according to race. The findings warrant further investigation," the authors write.

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