Parents play a prominent role in molding the adult their children become, and new research suggests this is true for health as well as character. A study has found children exposed to their parents' smoking are at a greater risk of developing heart disease in adulthood than the children of nonsmoking parents.

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Parents can reduce their children's risk of heart disease by not smoking in the home and smoking well away from their children.

The new study, published in Circulation, adds to the growing evidence demonstrating that parents smoking can have a long-term effect on their children's cardiovascular health.

"To gain more insight on the long-term harms of passive smoke exposure in early life, we undertook the first investigation of whether parental smoking and smoking hygiene in childhood is related to the presence of carotid atherosclerotic plaque in adulthood," write the authors.

For the study, the researchers followed participants in the Cardiovascular Risk in Young Finns Study - a prospective study conducted across five major cities in Finland, designed to examine the early-life risk factors of cardiovascular disease.

In 1980 and 1983, information was collected on childhood exposure to parental smoking. Carotid ultrasound data were collected when the participants had reached adulthood in 2001 or 2007.

In 2014, the researchers then measured the childhood blood cotinine levels of the participants, using samples collected and frozen in 1980. Cotinine is a major breakdown product of nicotine and can be used as a biomarker for exposure to secondhand smoke.

The researchers found that 84% of children from households where neither parent smoked had nondetectable cotinine levels in their samples. In contrast, only 62% of children from households where one parent smoked and 43% of children from households where both parents smoked had blood samples with nondetectable cotinine levels.

Heart disease risk can be lessened by exercising 'good smoking hygiene'

Regardless of other variables, the risk of developing plaque in the carotid artery in adulthood was 1.7 times higher in participants who had been exposed to at least one parental smoker as a child compared with those whose parents had not smoked.

The risk of developing carotid plaque also depended on whether the smoking parents attempted to limit their children's exposure or not. In children whose parents smoked but appeared to limit the child's exposure, the risk was 1.6 times higher than children whose parents did not smoke.

In contrast, children whose parents smoked but did not appear to limit their child's exposure to smoke faced a risk of carotid plaque developing that was four times greater than those whose parents did not smoke.

"Although we cannot confirm that children with a detectable blood cotinine [level] 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," says lead author Costan Magnussen, of the University of Tasmania, Australia.

The findings suggest that the children of parents that smoke have an increased risk of cardiovascular disease in adulthood, although this risk can be lessened by parents exercising good smoking hygiene - not smoking in the vicinity of children, for example.

"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)," states Magnussen.

However, in order to ensure the best long-term cardiovascular health for their children, parents should quit smoking altogether. The authors conclude it is important that parents are informed of the effects their smoking can have on their child's health, both in the short- and long-term.

Recently, Medical News Today reported on a new series published in The Lancet in which an international group of health and policy experts call for the United Nations to lead efforts toward a world essentially free from tobacco products.