June 08--These days, it should come as no surprise to anyone that exposure to tobacco smoke is unhealthy. Many studies have linked secondhand smoke to respiratory problems, asthma, sudden infant death syndrome, middle ear infections and other physical health problems.
But perhaps the most convincing study, which was recently published in the Archives of General Psychiatry, showed that exposure to secondhand smoke has a direct, measurable impact on the brain -- and the effect is similar to what happens in the brain of the person doing the smoking.
"Children and adults riding in car with someone who smokes has the nicotine go to their brain just like a smoker," said Dr. Todd Mahr, a Gundersen Lutheran specialist in children's allergies and asthma.
"Smoking in a car even with a cracked open window will cause harm to others," he said.
The evidence is so strong because the study used positron emission tomography (PET), Mahr said.
PET is a nuclear medicine imaging technique that produces a three-dimensional image or picture of functional processes in the body.
The PET scans in the study showed that one hour of secondhand smoke in an enclosed space results in enough nicotine reaching the brain to bind receptors that are normally targeted by direct exposure to tobacco smoke.
"And that happens in the brain of both smokers and nonsmokers," said Mahr, a longtime leader of a La Crosse County smoke-free workplace coalition.
"This is the strongest evidence because it shows the smoke gets to the brain pretty quickly," Mahr said.
People want to believe that secondhand smoke is just a nuisance.
"These results show that even limited secondhand smoke exposure delivers enough nicotine to the brain to alter its function," said Dr. Nora D. Volkow, director of the National Institute on Drug Abuse. "Chronic or severe exposure could result in even higher brain nicotine levels, which may explain why secondhand smoke exposure increases vulnerability to nicotine addiction."
The study, funded by the National Institute on Drug Abuse, part of the National Institutes of Health, also showed exposure to this secondhand smoke evokes cravings among smokers.
Previous research has shown that exposure to secondhand smoke increases the likelihood that children will become teenage smokers and makes it more difficult for adult smokers to quit. Such associations suggest that secondhand smoke acts on the brain to promote smoking behavior.
"This research is perfect for me to help talk to smoking parents who have a child with asthma," Mahr said. "It also supports that exposure to secondhand smoke makes children become more vulnerable to becoming a smoker.
"It's just one more thing to talk to parents about, and not only about their modeling behavior," he said.
The recent research provides substantial evidence to support policies that ban smoking in public places, particularly in enclosed spaces and around children, according to Paula Silha, co-coordinator of the 7 C's Health Initiative, a tobacco prevention coalition serving seven area counties.
"Many people still think it is a smell issue and not a health issue," Silha said. "It's scary to me how a small amount of secondhand smoke can impact the heart muscle and now the brain."
Mahr also said another recent study showed that pregnant women who live or work with smokers may be at a slightly higher risk of having a stillbirth.
Newborns also weigh a little less and had smaller heads if their mothers were exposed regularly to secondhand smoke in a study published in an international journal of Obstetrics and Gynecology.
"It's great to get a pregnant woman to stop smoking, but it makes a case for the husband or family members to also quit smoking," Mahr said.
Still, another recent study showed children and teens exposed to secondhand smoke are more likely to develop symptoms for a variety of mental health problems, including major depressive disorder, attention-deficit/hyperactivity disorder and others.
The study published in the journal Archives of Pediatrics and Adolescent Medicine, is believed to be the first that looks at how secondhand smoke exposure -- as measured by the presence of a nicotine metabolite in the blood -- is associated with mental health in a nationally representative sample of American kids and teens.
"All the research is overwhelming, and it is clear that people should reduce their exposure to secondhand smoke," Silha said. "That means staying away from smokers."
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