Smoking tied to kids' behaviour problems
2011-07-14 14:02
New York - Children exposed to second-hand smoke at home may be more likely to have learning and behavioural problems, according to a US study.
Of more than 55 000 US children younger than 12 years, 6% lived with a smoker - and those children were more likely to have ADHD compared to children in smoke-free homes, the study, published in Paediatrics, found.
Even after accounting for a number of possible explanations, such as parents' income and education levels, second-hand smoke was still tied to a higher risk of behavioural problems, said Hillel Alpert at the Harvard School of Public Health, one of the researchers.
The findings don't prove a smoke-filled home is to blame, because there are other factors that the study didn't look at that may also be to blame - but it may give parents yet another reason to keep their homes smoke-free.
Health experts already recommend that children be shielded from second-hand smoke for health reasons, since it can increase their risk of respiratory infections, severe asthma and sudden infant death syndrome.
Increased risks
"The key message for parents is to protect their children from exposure to second-hand smoke," said Alpert.
One other factor to consider is that children exposed to second-hand smoke often had intra-uterine exposure as well, which has been linked to increased risks of learning and behavioural problems.
It's also possible that parents who smoke have a greater history of learning or behaviour problems themselves compared with non-smoking parents.
The results are based on a 2007 national survey of parents of 55 358 children younger than 12. The finding that 6% lived with a smoker translates into nearly five million US children exposed to second-hand smoke at home, according to the research team.
About 20% of parents in smoking households said their child had at least one type of conduct disorder, versus less than 9% of parents in non-smoking homes.
When Alpert's team accounted for poverty, race, mothers' education levels and other factors, second-hand smoke was tied to a 51% increase in a child's risk of having one of the three disorders.
The researchers said that it's unclear exactly how second-hand smoke would contribute to learning and behavioural problems. Some research has speculated that the smoke may affect certain chemicals in children's developing brains.
A second study in Paediatrics suggested that children's reactions to their parents' second-hand smoke may also play some role in their own likelihood of taking up the habit.
Among 165 low-income preteens from smoking households, those who thought second-hand smoke was "unpleasant or gross" were 78% less likely than other children to be at a high risk of smoking.
Alpert said that whatever the reasons for the current findings, they underscore the need for children to be kept away from smoke.
"We still have five million children exposed to second-hand smoke at home," he said.
"A lot of progress has been made in reducing that number, but there's still a lot left to be done."