Our analysis showed that the longer adolescents are exposed to a parents smoking when the parent is addicted to nicotine, the more likely they are to begin smoking and to become regular smokers in the future, said lead author Darren Mays.
Quitting is of course important for parents health, and could be important for kids health too, said Mays, a public health researcher with the Cancer Prevention & Control Program at the Lombardi Comprehensive Cancer Center of Georgetown University Medical Center in Washington, D.C.
Our results suggest that for parents who are addicted smokers (quitting) may also reduce the likelihood that their children will go on to become smokers in the future, he told Reuters Health.
For the study, Mays and his colleagues followed 400 teens from early to late adolescence. Researchers separately interviewed the kids, most around age 14, and one of their parents, about their respective smoking histories.
The kids were interviewed again one year later and again four years after that.
Six percent of the kids were already regular smokers when the study began. Thirty percent of the kids reported at all three interviews that they had never smoked.
The rest of the kids either experimented with a few cigarettes early on - nearly half of whom became regular smokers by year five - or experimented later on.
Teens whose parents were current smokers and addicted to nicotine were 10 times more likely to themselves become regular smokers at an early age or to experiment early on with cigarettes than kids with nonsmoking parents.
Among the parents who were current smokers, each year they had smoked slightly increased the odds that their kids would end up in a heavy-smoking trajectory.
The results don't prove that parents smoking caused their kids to take up the habit, the study team acknowledges.
But theres no real debate about whether there is a link between parental and child smoking researchers are confident that they are connected, probably due to a combination of genetics and social norms in the household, the researchers note in their report, published in Pediatrics.
Of the 24 kids who were already regular smokers at age 14, two-thirds had a parent who was a current smoker, compared to 3 with a parent that was a former smoker and 5 with nonsmoking parents.
There is strong evidence of this relationship for both tobacco and alcohol, said Mike Vuolo, associate director of the Center for Research on Young Peoples Health at Purdue University in West Lafayette, Indiana. He was not involved in the new study.
This new research focuses specifically on nicotine dependence, which is substantively important, Vuolo told Reuters Health by email.
There is solid evidence that genetics explains the link between parent smoking and child smoking, said Jonathan Bricker of the Fred Hutchinson Cancer Research Center in Seattle, Washington.
But what makes this study and others like it so important is that it identifies something practical and important we can do right now: help parents quit smoking for the sake of their children, Bricker told Reuters Health by email.
It might be a good idea to target quit-smoking initiatives at parents who are hooked on nicotine, not just those who smoke, he added.
But in terms of nicotine dependence, the new study contradicts previous research by the same team on the same subject, according to Denise B. Kandel, a professor of sociomedical sciences at Columbia University Mailman School of Public Health in New York.
The earlier analysis found that onset of smoking was the same whether or not parents were dependent on nicotine, Kandel told Reuters Health by email.
By that logic, whether or not parents smoke at all is the important measure, not their dependence on nicotine.
The results are still important for public health advocates, who can identify children at high risk of smoking by whether or not their parents smoke, she said.
The best advice for any parent who smokes is to quit as soon as possible and that resources such as their family doctor, telephone quit lines and online programs are available to help, Mays said.