Tobacco smoke may harm children’s kidneys

Adolescents exposed to tobacco smoke, whether through actively smoking or secondhand smoke, may show markers of kidney disease, according to a study from Johns Hopkins Bloomberg School of Public Health and the Johns Hopkins Children’s Center.

Using data for 7,516 adolescents aged 12 to 17 years from the National Health and Nutrition Examination Survey 2009-2010, researchers assessed tobacco use and exposure to secondhand smoke through self-reported home questionnaires and measures of serum cotinine, a biomarker of tobacco exposure.

The investigators defined active smokers as those adolescents who reported smoking “at least one day” or smoking “at least one cigarette” in the last month and also those with serum cotinine levels higher than 10 ng/ml. Adolescents who reported living with a person who smoked or who had cotinine levels from 0.05 ng/ml to 10 ng/ml were classified as exposed to secondhand smoke. Participants with cotinine levels below 0.05 ng/ml, not living with a smoker, and not smoking in the last month, were classified as unexposed to tobacco.

Data showed that compared with unexposed children, adolescents who smoked or who were exposed to secondhand tobacco smoke demonstrated a lower estimated glomerular filtration rate, a measure of kidney function, which decreased linearly with increasing concentrations of serum cotinine. The association was stronger in boys and in children whose parents had less education, possibly because these parents were more likely to be active smokers.

The researchers acknowledge that their study results could be limited by unmeasured factors, such as participants’ exposure to other toxic substances and differences in nutrition and access to health care. However, their findings modestly support that tobacco smoke may affect kidney function early in life.

More than 600,000 US middle school students and 3 million high school students smoke cigarettes, and 15% of nonsmoking adolescents report they are exposed to secondhand smoke at home. Protecting young people from active smoking is essential because nearly 90% of adults who smoke began by the time they were 18 years old.