Lead author Jill Baumgartner, a research fellow at the University of Minnesota's Institute on the Environment, says the study showed girls the same ages exposed to secondhand smoke had lower blood pressure than girls who were not exposed to tobacco smoke.
"These findings support several previous studies suggesting that something about female gender may provide protection from harmful vascular changes due to secondhand smoke exposure," Baumgartner says in a statement. "An important next step is to understand why."
Baumgartner and colleagues analyzed data from four National Health and Nutrition Examination Surveys conducted from 1999 to 2006 by the U.S. Centers for Disease Control and Prevention.
They assessed 6,421 youths' exposure to secondhand smoke from the subjects' own reports of whether they lived with a smoker and through participants' levels of cotinine -- a substance produced when the body breaks down nicotine.
The findings suggest the cardiovascular effects of tobacco smoke exposure may begin very early in life. It is not known whether these changes are reversible if children are removed from smoke exposure.
The study was presented at the Pediatric Academic Societies annual meeting in Denver.