Teens of a parent who smoked even if the mother or father quit before the teen was born are more likely to smoke than those whose parents are non-smokers, a new study finds.
Having an older brother or sister who smokes also raises the odds that a teen will pick up the habit, the researchers report.
"These findings imply that any amount of smoking could have important influences on the next generation," said lead researcher Mike Vuolo, an assistant professor of sociology at Purdue University. "Given the influence on the oldest siblings, this is especially the case in heavy-smoking households."
Vuolo and co-author Jeremy Staff, an associate professor of sociology at Pennsylvania State University, analysed data from a multigenerational study that has followed participants since 1988, when they were freshmen in high school, to 2011. They focused on 214 now-parents and 314 of their children aged 11 and older.
Annual survey results uncovered four patterns of smoking: teens who were persistent heavy smokers, teens who were light smokers who quit or reduced use, teens who started smoking later and non-smokers.
Their children were then surveyed in 2011.
"Surprisingly, we found similar odds of smoking among the children for the three smoking groups [23% to 29%] compared with children of non-smokers [8%]," Vuolo said.
In homes with a persistent heavy-smoking parent, the oldest sibling is influenced to smoke, which in turn increases the chances that younger siblings will smoke by six times, he added.
"We should educate young people that smoking at any time in their lives could influence their children. Also, preventative efforts should target heavy-smoking households, trying to break the cycle of influence on the oldest siblings," Vuolo said.
The report was published online on 5 August and in the September print issue of Pediatrics.
Dr John Spangler, a professor of family and community medicine at Wake Forest Baptist Medical Center, said there may well be a genetic component to these findings.
"This study confirms what we have already sensed, that there is a family history of tobacco use among many smokers," Spangler said. "We know that people are more likely to uses substances like alcohol based on family history, the same holds true for tobacco use."
This may point to a genetic predisposition to metabolise nicotine or dopamine differently, he said.
"We should encourage doctors to ask about a family history of smoking, because if there is a family history of smoking then that individual is more likely to be a smoker in the future," Spangler said.
Parents who are former smokers should realise their child is more likely to become a smoker. These parents may want to discuss smoking with their children with an eye toward preventing it.
"This may also be a good way for physicians to counsel parents about and children about tobacco use that there is this risk factor," Spangler said.
Another expert agreed that parents who smoke should make every effort to quit, but said that further measures are needed.
"Consistent with previous research, this study shows the dramatic impact of parental smoking on youth smoking," said Danny McGoldrick, vice president for research at the Campaign for Tobacco-Free Kids.
"Even parents who are unable to quit should make their cars and homes smoke-free, send clear messages to their children about not smoking and support policies and programs like increased tobacco taxes, smoke-free laws and comprehensive prevention and cessation programs that are proven to reduce smoking among kids and adults," he said.
While the study showed an association between having parents or siblings who smoke and smoking yourself, it did not prove a cause-and-effect link.
Another study in the same journal issue found that 72% of teens who use smokeless tobacco products also smoke cigarettes.
This finding runs counter to the idea that smokeless tobacco products can help reduce the health problems associated with tobacco use, the researchers said.
Kids who used smokeless tobacco were more likely to believe that it's less harmful than tobacco products in general, the study found.
For facts about smoking cessation, visit the U.S. Centers for Disease Control and Prevention.