Passive smoking may raise blood pressure in boys.

Passive smoking can raise blood pressure levels in boys, scientists have found. This will put them at higher risk in later life of hypertension – which is itself associated with a greater chance of developing heart and kidney disease.  In her study, Jill Baumgartner of the University of Minnesota's Institute on the Environment looked at more than 6,400 children aged eight to 17 who had been exposed to secondhand tobacco smoke. She found an average rise of 1.6 mmHg – or a 1% increase on average healthy levels – in the systolic blood pressure of boys who had been exposed to secondhand smoke compared to boys who had not.

"For that individual child, it won't have a huge impact," said Mike Knapton, associate medical director at the British Heart Foundation. "But, if you've got two million kids with a 1% increase, you start to see changes in the prevalence of respiratory disease, heart disease and cancer."  Baumgartner, who presented her work on Sunday at the annual meeting of the Paediatric Academic Societies in Denver, Colorado, said more than a third of children in the US and globally were exposed to secondhand smoke levels similar to those associated with adverse cardiovascular effects in her study.

Previous research has linked secondhand smoke and increased blood pressure in adults, but the effect had not been measured in children.  Systolic pressure is the maximum during a heartbeat and measures the surge of blood when the heart contracts. A healthy level in adults is about 120mmHg but the level changes for children as they grow older. Knapton said a one-month-old child's average systolic blood pressure was 60mmHg, rising to 115mmHg at 15.

"We know blood pressure tends to track upwards as you get older – my blood pressure will be greater now than as a child," he said. "The higher you start, the higher it gets to when you're an adult and we know that, in adults, high blood pressure is a risk factor for heart disease.

"The assumption might be that, if you're pushing your children's blood pressure up in childhood, that will put them at greater risk of blood pressure as an adult, which will put them at higher risk of heart disease and stroke."  Baumgartner's work showed that, unlike boys, girls exposed to secondhand smoke had lower systolic blood pressures than girls who were not – by 1.8 mmHg on average.

"These findings support several previous studies suggesting that something about female gender may provide protection from harmful vascular changes due to secondhand smoke exposure," she said. "An important next step is to understand why."

The researchers collected information on passive smoking from questionnaires conducted by the US Centres for Disease Control and Prevention between 1996 and 2006. The surveys collected information on which children lived with smokers and also on the levels of cotinine in a child's blood, which is a byproduct of the metabolism of nicotine by the body and seen as a reliable marker for exposure to tobacco smoke.
Baumgartner said the relationship between secondhand smoke exposure and blood pressure observed in her study provided "further incentive for governments to support smoking bans and other legislation that protects children from secondhand smoke".

Knapton said passive smoking was only part of the story. "There has been an association between cot death and smoking in the home – 86% of cot deaths occur in families where the mother smokes," he said.
"We know that children from families that smoke are more likely to smoke themselves. Children who live with two adult smokers are four times more likely to be smokers themselves than children who live with non-smokers."

Source: The Guardian