Exposure to environmental tobacco smoke (ETS)–”second-hand smoke”–is associated with mildly to moderately depressed scores on tests of math, reading, and visuospatial skills as compared to children who lacked such exposures. Even low levels of exposure to ETS were associated with lower scores on the reading and math sections of the Wide Range Achievement Test (WRAT) and the block-design subtest of the Wechsler Intelligence Scale for Children-III (WISC-III) (but not with scores on the digit-span section of the WISC-III).
A team led by Kimberly Yolton of the University of Cincinnati College of Medicine and Cincinnati Children’s Hospital Medical Center analyzed data about 4,399 6-16 year olds from the Third National Health and Nutrition Examination Survey. They excluded some children, especially those who reported smoking. Rather than counting on subjective reports of smoke in children’s environments, they correlated levels of cotinine in the children’s blood with their performance on the tests. (Cotinine is a metabolite of nicotine.)
Yolton and colleagues adjusted for childrens’ sex, race, region, poverty, parent education and marital status, and blood levels of iron; the correlations between ETS and performance on the WRAT and WISC-III emerged even when these factors were taken into account. It’s possible that some other factors, especially parental cognitive abilities and quality of home environment, play a role in the lower WRAT and WISC-III scores. The research team was not able to control for these latter factors.
- Report of the study by Yolton, Dietrich, Auinger, Lanphear, & Hornung in Jan 2005 Environmental Health Perspectives, 113(1).
- News story in Jan 2005 Environmental Health Perspectives.
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