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BALTIMORE -- Children were more likely to have increased blood pressure, and a higher risk for hypertension, if they were exposed to tobacco-specific metabolites found in secondhand smoke, researchers reported here.

Among boys, the carcinogen 4-(methyl-nitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) was associated with increased diastolic blood pressure (DBP) but not systolic blood pressure (SBP) after adjusting for race or ethnicity, ratio of family poverty to income, waist circumference, cadmium and lead exposure, first albumin creatinine ratio, and urinary creatinine, according to Karen Wilson, MD, MPH, of the Icahn School of Medicine at Mount Sinai in New York City, and colleagues.

For girls, exposure to NNAL was linked to increased SBP percentiles, but not DBP percentiles, they reported at the Pediatric Academic Societies annual meeting.

Overall, children had significantly higher odds of being hypertensive if they were in the 75th percentile of secondhand smoke exposure versus the ≤25th percentile, Wilson reported.

"It's important to remember that secondhand smoke does not just affect the respiratory system; it can affect the cardiovascular system, and hypertension and increased blood pressure are just early warning signs of that," Wilson told MedPage Today. "Certainly, the effects of tobacco smoke exposure can last through adulthood."

Prior research has linked exposure to secondhand smoke in childhood to increased risk of childhood cancers, neurobehavioral disorders, and preclinical atherosclerosis, according to the on protecting children from exposure to tobacco smoke.

Although some studies have found a link between childhood increased BP and cotinine, another marker for secondhand smoke, Wilson and colleagues wanted to determine whether NNAL, a , had similar effects. NNAL has a longer half life than cotinine (10-16 days vs 16-18 hours) and can measure exposures that happen more intermittently across different periods of time, she said.

"The implications of elevated blood pressure in early adolescence for adult outcomes are significant because, most of the time, a child who is gaining weight normally has good nutrition and is in a reasonably supportive environment [and] would not have a specific risk factor for hypertension," commented Francis Sessions Cole III, MD, of the Washington University School of Medicine in St. Louis, who was not involved with the study.

Wilson's group measured secondhand smoke exposure through serum cotinine and urine NNAL collected from adolescents, ages 8 to 17, who participated in the from 2007 through 2012. Hypertensive status was defined as at least the 90th percentile of BP, or 120/80 for children ages <13 years and at least 120/80 for children ages ≥13 years.

More than half of the children evaluated were white (56%), while 22% were Hispanic, and 14% were black. Half were male (50%) and the mean age was 12.1 years.

The average NNAL concentration across the group was 1.60 pg/mL; the mean cotinine concentration was 0.06 ng/mL. This varied significantly by race or ethnicity, with Hispanic and black children generally being more likely to be exposed to the metabolites. Children with smoking occurring in the home (13.9%) were also more likely to have been exposed to them, the authors reported.

Increased levels of serum cotinine were also associated with an increase in DBP, but not SBP percentiles, Wilson reported. By sex, increased cotinine was associated with increased DBP in boys, but not girls, she added.

In addition to the potential for confounding variables based on the NHANES questions, the cross-sectional design and lack of longitudinal data were study limitations. Also, the authors were not able to reach conclusions on temporality or causation of exposure and outcome.

Cole told MedPage Today that possible confounding variables like environmental exposures impacted the results, but overall, the research successfully leveraged a large cohort of children with reliable indicators of secondhand smoke exposure. As such, it has the potential to inform future interventional studies that examine efforts to reduce exposure most effectively, he said.

"If you have a genetic risk for hypertension, that's a whole different set of interventions, but secondhand smoke has nothing to do with developing a drug, or testing multiple pathways for hypertension," Cole said. "This is about going outside to smoke or changing your clothes to hold your baby -- these aren't wildly expensive or difficult kinds of interventions."

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