THURSDAY, March 13 (HealthDay News) -- Secondhand smoke causes signs of cardiovascular damage in children, especially the very youngest, new research contends.

The findings, which focused on children from 2 to 14 years old, showed that environmental tobacco exposure (second-hand smoke) caused increased markers of inflammation and signs of vascular injury, suggesting an increased risk of heart disease. The youngest children appeared to be more affected than teens.

"Toddlers are smokers by default," said one of the study's authors, John Bauer, director of the Center for Cardiovascular Medicine at Nationwide Children's Hospital and Research Institute in Columbus, Ohio. "Forty percent of toddlers in our study had nicotine content that in adults would suggest that they were active smokers. But, an active smoker has a filter on cigarettes. The toxicity from smoke that is inhaled in the atmosphere is worse because there's no filter."

Results of the study were to be presented Thursday at the American Heart Association's Cardiovascular Disease Epidemiology and Prevention meeting, in Colorado Springs.

Bauer and his colleagues took hair and blood samples from 125 children. Fifty-seven were between the ages of 2 and 5; 68 were between 9 and 14. Hair samples were used to measure nicotine exposure, and blood samples were used to look for a type of cell called an endothelial progenitor cell (EPC). These cells replenish the endothelium (the lining of the blood vessels) and provide clues to levels of cardiovascular health.

The researchers also asked the parents how many smokers children had been exposed to in a 24-hour period.

Children in the youngest age group had almost six times the average nicotine levels than older children did. Toddlers had an average nicotine level of 12.68 nanograms per milligram of hair, while older kids had an average level of 2.57 nanograms per milligram.

"Toddlers were more exposed," Bauer said. "Toddlers are like fish in a fish bowl. They're strapped pretty closely to their parental units, which exposes them to more smoke than adolescents who live in the same set of circumstances."

"Toddlers also breathe more rapidly, so they inhale more," added one of Bauer's co-authors, Dr. Judith Groner, a pediatrician and ambulatory care physician at Nationwide.

The youngest children also had higher levels of an inflammatory marker called soluble intracellular adhesion molecules, and there was an inverse relationship between EPC levels and exposure to smoke in both age groups, though again, the effect of secondhand smoke was more pronounced in the younger children.

These findings are similar to what has been found in adult smokers, according to the study authors. EPC levels haven't yet been studied in adults exposed to secondhand smoke.

"Based on markers of vascular stress, toddlers are hit harder," said Bauer. "To what extent this is reversible if exposure is stopped isn't known. In adults, there is evidence that when active smokers quit smoking that the risk of heart disease is lower, but some research suggests that cardiovascular disease may be imprinted in early life, so we don't know if this is reversible or not."

"This study suggests that if you have a toddler, make sure they're out of harm's way," he added.

Dr. Devang Doshi, director of pediatric pulmonology, allergy and immunology at Beaumont Hospital in Royal Oak, Mich., said, "This study gives us more insight into the bad effects of secondhand smoke exposure from a respiratory and cardiac standpoint."

"A lot of people don't realize that when you smoke in the house, children are continuously exposed. It's always in the house; the smoke doesn't just go away," he added.

Doshi said his first advice to parents is to quit smoking. Failing that, he said he advises parents to go outside, away from the house to smoke, and to wear at least two layers of clothing. Then, when they come back in the house, he recommends removing the top layer of clothing and washing your hands to try to limit your child's exposure.

"Don't smoke," advised Groner, "and have a total ban on smoking around your child."

More information

To learn more about the effects of secondhand smoke, visit the American Lung Association.

SOURCES: Judith Groner, M.D., pediatrician and ambulatory care physician, and John Bauer, Ph.D., director, Center for Cardiovascular Medicine, Nationwide Children's Hospital and Research Institute, Columbus, Ohio; Devang Doshi, M.D., director, pediatric pulmonology, allergy and immunology, Beaumont Hospital, Royal Oak, Mich.; March 13, 2008, presentation, American Heart Association Cardiovascular Disease Epidemiology and Prevention annual meeting, Colorado Springs, Colo.