Environmental Link to Childhood Hypertension Established

Brian Hoyle

May 31, 2011 (Denver, Colorado) — A study involving more than 6400 youth has linked exposure to environmental tobacco smoke — popularly dubbed secondhand smoke — to increased blood pressure in boys. The increase was not evident in girls, adding to the evidence of a sex-specific response to some environmental cues.

The results of a study that assessed a series of National Health and Nutrition Examination Survey (NHANES) data were presented here at the Pediatric Academic Societies and Asian Society for Pediatric Research 2011 Annual Meeting by Jill Baumgartner, PhD, a research fellow at the Institute on the Environment, University of Minnesota, Minneapolis.

Elevated blood pressure early in life can be a harbinger of adult hypertension, which has been linked to heart and kidney disease and is the third leading cause of illness and death globally. In nonsmoking adults, studies have confirmed the association between secondhand smoke and increased blood pressure. However, little is known about the effects of secondhand smoke on blood pressure in children.

"This study adds to the evidence that environmental tobacco smoke has a cardiovascular effect even at a very young age," Dr. Baumgartner told Medscape Medical News.

The researchers analyzed the cross-sectional data obtained from 4 NHANES surveys conducted between 1999 and 2006. Subjects were 6421 youth who lived with at least 1 adult who smoked, determined by self-reporting and the detection of serum cotinine levels of 0.01 to 14.00 ng/mL.

"Cotinine is a metabolite of nicotine and is considered to be the best biological marker of exposure to tobacco smoke," Dr. Baumgartner explained.

Data were matched for the year of the particular NHANES survey and for blood pressure risk factors, including sex, body mass index for age percentile, and physical activity. Weighted linear regression was used to estimate the influence of secondhand smoke on blood pressure.

Of the 6421 subjects, 2976 were female, 16% were clinically overweight, and 21% were clinically obese.

A strong effect for sex was evident. Boys 8 to 17 years of age who were exposed to secondhand smoke had a systolic blood pressure that was significantly higher (1.6 mm Hg; 95% confidence interval [CI], 0.8; P < .001) than their counterparts from nonsmoking households.

In striking contrast, Dr. Baumgartner said, girls living with a smoker had lower systolic blood pressure (1.8 mm Hg; 95% CI, –2.5 to –1.7; P < .001). The results were supported by measurements of cotinine levels.

There was no consistent relation between secondhand smoke and diastolic blood pressure.

"The increased blood pressure observed in boys in our study has important implications for populations. Over one third of American children, and globally, are exposed to secondhand smoke, similar to that which produced the cardiovascular effects in this study," Dr. Baumgartner told Medscape Medical News.

Whether the blood pressure change can be reversed in a smoke-free environment is not known. But, say the researchers, the study indicates the importance of restricting the exposure of children, especially boys, to secondhand smoke.

"These are important results. I realize it is normal in such studies to measure blood pressure once. However, blood pressure being dynamic, information could be missed by a single measurement," Sven Cnattingius, MD, professor of reproductive epidemiology, Department of Medicine, Karolinska Institutet, Solna, Sweden, told Medscape Medical News.

The effect of sex was of particular interest.

"I wonder about the gender effect concerning blood pressure. Maybe factors like testosterone could be at play," James Campbell, MD, from Rochester General Hospital in New York, told Medscape Medical News.

Dr. Baumgartner explained that previous studies have shown an effect of sex in other physiological aspects. These findings suggest to the researchers that something in females is protective of vascular changes due to secondhand smoke.

The researchers have disclosed no relevant financial relationships.

Pediatric Academic Societies (PAS) and Asian Society for Pediatric Research 2011 Annual Meeting: Abstract 2805.5. Presented May 1, 2011.