SEATTLE — May 7, 2003 — New findings from the Fred Hutchinson Cancer Research Center may provide a compelling reason for smoking parents of young children to kick the habit. Researchers have found that parents who quit smoking before their child reaches third grade will significantly reduce their child's odds of becoming a smoker by the time their senior year of high school rolls around.
Specifically, if one parent quits by the time the child is 8 or 9, the child's odds of being a daily or monthly smoker at age 17 or 18 decrease by 25 percent. If both parents quit, the child's chances of smoking drop by nearly 40 percent, according to Jonathan B. Bricker and colleagues at Fred Hutchinson and the University of Washington, who report their findings in the May issue of the journal Addiction, a publication of the United Kingdom-based Society for the Study of Addiction.
"Statistics show that if a child reaches age 18 without becoming a smoker, his or her odds of remaining smoke-free are around 90 percent. Therefore, our results indicate that if all smoking parents were to quit by the time their children were around age 8, it could prevent 136,000 young people in the United States from becoming daily, long-term smokers," said Bricker, a research associate in the Cancer Prevention and Trials Program of Fred Hutchinson's Public Health Sciences Division.
The most surprising finding of the study, Bricker said, was that parental influence on smoking was not affected by the child's age when the last parent quit, as long as the parents quit by the time the child was 8 or 9. "It didn't matter whether one or both parents quit when the child was a baby, a toddler or in third grade," Bricker said. "The most important thing was that they quit." More research is needed, however, to determine the benefits, if any, of parental-smoking cessation after children are 8 or 9.
There also was no evidence that parent or child gender had any impact on the link between parental-smoking cessation and children's smoking behavior; mothers were no more influential than fathers and girls were no more susceptible than boys.
Not surprisingly, those least likely to smoke were the children of parents who had never taken up the habit. Smoking prevalence in 12th grade was 14 percent when neither parents had ever smoked as compared to 37 percent when both parents were current smokers and 26 percent when both parents had quit by the time the child was in third grade.
The findings are based on data collected from more than 3,000 children and parents in 20 school districts in Washington. Information on parents' smoking behavior was collected when the children were in the third grade (8 or 9 years old), and information on children's smoking behavior was collected nine years later, when the children were in 12th grade (17 or 18 years old). Student self-reports of smoking activity were found to be largely accurate as verified through saliva tests that checked for the presence of cotinine, a by-product of nicotine.
"This study is unique because it is the first prospective study to follow a large group of parents and children over time to examine the relationship between parental-smoking cessation when children are young and how it relates to smoking behavior in late adolescence," Bricker said.
Nearly half (49 percent) of the children were female and the overwhelming majority (91 percent) where white. "One limitation of the study is that our sample was almost all Caucasian, so the results may not generalize to a multiethnic community," Bricker said. Another limitation is that the study did not directly look at the impact of family income or education on smoking behavior, although the socioeconomic status of each school district was taken into account during data analysis.
The study also did not take into account the impact of parental-smoking relapse. "Of parents who quit for a year, nearly 40 percent eventually will relapse. So we think we're actually underestimating the impact of parental-smoking cessation on their children's smoking activity, because we didn't exclude parents who relapsed, which actually may have watered down the findings," Bricker said. "Looking at parental quitting and relapse after the child is 8 would be valuable to understand whether there are any potential benefits of quitting — or potential downsides of relapse — when children are adolescents."
The students in the study served as the control, or comparison, group for the landmark Hutchinson Smoking Prevention Project, the largest and longest school-based intervention trial ever conducted in smoking-prevention research. Overall the study involved 8,400 students and 600 teachers throughout 40 school districts in Washington. Results of this 15-year study, funded by the National Cancer Institute, were published in 2000.
The study found that implementation of a school-based prevention program focused on teaching youth how to identify and resist social influences to smoke — the main thrust of smoking-prevention education and research for more than two decades — simply doesn't work.
While the results were surprising, the data remain a rich resource for further analysis with regard to parental influences on smoking behavior, among other factors.
"We now have the luxury of being able to look at the control-group, or non-intervention, data from this huge study and answer some compelling scientific questions that are of great public-health and clinical relevance, not only to parents but also to professionals who intervene with children to help prevent them from smoking," Bricker said.
For example, the results of this study suggest that it may be beneficial to include parents in primary smoking-prevention programs for children. "Prevention programs need to reach the parents as well as the children," Bricker said. "We need parents to realize that if they quit smoking, they could help their children from becoming daily smokers."
How and why are children impacted by parental-smoking cessation? Bricker and colleagues suspect it's largely because parents who've quit may engage in anti-smoking behaviors that reduce their children's overall exposure to cigarettes, from requesting nonsmoking sections in restaurants to banning smoking at home.
While more research into the mechanisms of parental influence is needed, researchers do know is that the window of vulnerability for smoking tends to open around age 8 and close around age 20. This "smoking-acquisition period" may be influenced by a combination of genetics, and parental and peer models of smoking. It also may stem from a child's desire to emulate adult behavior, Bricker said, although in reality, only about 25 percent of adults smoke.
"Because adolescence is a period in which children are developing an identity as an adult, they are, in a sense, trying on behaviors like trying on clothes — behaviors they think will make them feel like adults," said Bricker, who's also a doctoral candidate in clinical psychology in the UW Department of Psychology, College of Arts and Sciences.
Parents who would like to quit are encouraged to contact their primary physician for smoking-cessation guidance, Bricker said. Resources for free smoking-cessation assistance include:
"The first step to quit smoking is becoming personally motivated to quit," Bricker said. "This study could help tip the motivational balance for parents — or prospective parents — who want to take the next step and do something about their smoking behavior, if not for their own sake then for that of their child."
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Fred Hutchinson Cancer Research Center
The Fred Hutchinson Cancer Research Center, home of two Nobel Prize laureates, is an independent, nonprofit research institution dedicated to the development and advancement of biomedical technology to eliminate cancer and other potentially fatal diseases. Fred Hutchinson receives more funding from the National Institutes of Health than any other independent U.S. research center. Recognized internationally for its pioneering work in bone-marrow transplantation, the center's four scientific divisions collaborate to form a unique environment for conducting basic and applied science. Fred Hutchinson, in collaboration with its clinical and research partners, the University of Washington Academic Medical Center and Children's Hospital and Regional Medical Center, is the only National Cancer Institute-designated comprehensive cancer center in the Pacific Northwest and is one of 38 nationwide. For more information, visit the center's Web site at www.fhcrc.org.