New research now suggests that teens that are exposed to smoking by their parents could have a higher risk of developing heart disease in adulthood compared to those whose parents didn't smoke. According to researchers, children whose parents smoke had almost two times the risk of developing carotid plaque in adulthood than children of parents who did not smoke. What is most striking is that the risk remained elevated even if parents actively tried to limit their children's exposure.

The findings add even more data to a growing body of evidence that exposure to smoking from parents has a lasting effect on children's cardiovasculary health. For the study, researchers tracked participiants in the Cardiovascular Risk in Young Finns study. This study included childhood exposure to smoking from 1980 to 1983. In 2001 and 2007, researchers collected carotid ultrasound data on the children that had since grown into adulthood.

Researchers didn't stop there, however, and in 2014 measured participants' blood cotinine levels from samples that were frozen in 1980. Cotinine is a passive smoke exposure biomarker.

Researchers found that the percent of children with non-detectable cotinine markers were highest among households where neither parent smoked at 64%. This figure decreased slightly in households where only one parent smoked to 62%. However, the rate dropped dramatically in households where both parents smoked to 43% indicating a potential increase in risk of developing heart disease.

The risk of developing heart disease was 1.6 times higher in children whose parents smoked, but seemed to limit their exposure. In parents who smoked but didn't work to limit exposure, a child's risk of heart disease was four times higher compared to children of parents that did not smoke.

"Although we cannot confirm that children with a detectable blood cotinine in our study was a result of passive smoke exposure directly from their parents, we know that a child's primary source of passive smoke exposure occurs at home," lead author of the study and senior research fellow at the Menzies Institute for Medical Research, University of Tasmania in Australia, Costan Magnussen says.

Researchers went on to say that it is best not smoke but, "For parents who are trying to quit smoking, they may be able to reduce some of the potential long-term risk for their children by actively reducing their children's exposure to secondhand smoke (i.e., not smoking inside the home, car, or smoke well away from their children)," Magnussen says. "Not smoking at all is by far the safest option."