TUESDAY, Aug. 19, 2014 (HealthDay News) -- Smoking while
pregnant or around an infant has long been linked to development of
asthma and allergies in young children. Now, researchers have found
that the risk may persist into the teen years.
The study, which followed nearly 4,000 children in Sweden for 16
years, underscores the dangers of parental smoking, experts
"Exposure to second-hand smoke during pregnancy or infancy increases a child's risk of developing allergic disease even up to adolescence," said study researcher Jesse Thacher, a doctoral student at the Karolinska Institute in Stockholm.
Fetal exposure to cigarette smoking was linked with an overall
45 percent higher risk of getting asthma up until age 16, Thacher
For infants exposed to a parent's smoking, the risks of
developing asthma and allergic rhinitis (stuffy or runny nose) in
childhood or adolescence were 23 and 18 percent greater,
respectively. The risk for eczema (inflamed, irritated skin) was 26
"Increased risks for asthma and rhinitis were seen primarily in early childhood, whereas those for eczema occurred later in life," Thacher said.
Previously, it wasn't clear whether the risks for asthma and
allergies continued into the teen years, Thacher said.
The study, published online Aug. 18 in
Pediatrics, only found an association between second-hand
smoke and children's health problems, however. It wasn't designed
to show a cause-and-effect relationship.
Thacher asked parents of children born from 1994 to 1996 about
their smoking habits, other lifestyle information, and symptoms of
allergic diseases in their children during the course of the
About 13 percent of the mothers smoked during pregnancy.
Parental smoking during infancy was reported by more than 20
While the study included only Swedish children, ''it would be
reasonable to expect comparable results between U.S. and Swedish
children, because populations in these countries share similar
lifestyle, and tobacco smoke should affect children in the same
way," Thacher said.
Although fewer parents smoke around their children than in the
past, it remains a problem in both countries, Thacher said.
"Rates of parental smoking in the U.S. vary by state, but it's around 17 percent," he said.
Allergies aren't the only childhood concern related to
second-hand smoking. Second-hand smoke contains about 4,000
chemicals, according to the American Academy of Pediatrics. More
than 50 of those chemicals are known to cause cancer.
Smoking during pregnancy has also been linked with miscarriage,
premature birth, lower birth weight, sudden infant death syndrome
(SIDS) and learning problems.
The findings provide new information and also reinforce other
research, said Dr. Len Horovitz, a pulmonary specialist at Lenox
Hill Hospital in New York City, who wasn't involved in the
"There's no safe smoking," he said, "and there doesn't seem to be much safe second-hand smoking either."
People are less aware of the dangers of second-hand smoke
compared to direct smoking, Horovitz said. "I don't think the
message about second-hand smoke exposure has been hammered home,"
One strength of the study, Horovitz said, is the large number of
children and the long-term follow-up.
Exactly why second-hand smoke is linked with these health
problems isn't known, Horovitz said. "We can surmise it is some
sort of irritant or inflammatory process, but we don't really know
the mechanism," he said.
Smoke exposure during pregnancy may contribute to asthma risk,
for instance, by changes in lung growth or the health of the
airways, the researchers wrote.
To learn more about second-hand smoke dangers, visit the
American Academy of Pediatrics.
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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