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Secondhand Smoke Risk Underestimated

Study finds heart disease risk rises as much as 60%

THURSDAY, July 1, 2004 (HealthDayNews) -- While the debate rages on in many communities about bans on smoking in public places, a new study finds the health risks from breathing in secondhand smoke may be even more dire than previously predicted.

Researchers report in the online edition of the British Medical Journal that exposure to secondhand smoke may increase the risk of coronary heart disease by 50 percent to 60 percent.

"This [study] adds to evidence that passive tobacco smoke exposure is harmful, especially for people at high risk of vascular disease," said Dr. Peter Whincup, a professor of cardiovascular epidemiology at St. George's Hospital Medical School in London. And, he said, it "adds to the case for keeping passive exposure as low as possible."

Passive smoke has been linked to an increased risk of cancer, heart disease and respiratory infections, according to the American Cancer Society. Passive smoking also aggravates asthma, making attacks more severe and more frequent.

In 2001, Whincup and his colleagues began following up on 4,729 men who had participated in the British regional heart study between 1978 and 1980. The men had answered questionnaires about their smoking habits and had provided blood samples.

They were between the ages of 40 and 59 at the start of the study, and came from 18 different towns in the United Kingdom.

The researchers tested the blood samples for cotinine, a substance used to measure exposure to cigarette smoke. These levels give the researchers an idea of overall exposure to passive smoke, but they didn't gather specific data about the source of the exposure.

The researchers then compared the cotinine levels to causes of death, and for those still living, to the incidence of heart disease and stroke.

"High overall passive smoking exposure seems to be related to an increase of about 50 percent in coronary heart disease," said Whincup. "This increase is greater than that seen with partner smoking."

The researchers also reported that the greatest increase in risk occurred during the first and second five year follow-up periods of the study. There was no statistically significant association between stroke and passive smoking.

"This study provides us with a more accurate and more alarming view of the association of breathing in secondhand smoke and coronary artery disease," said Thomas Glynn, director of cancer science and trends at the American Cancer Society. "And while they didn't look at cancer rates, I wouldn't be surprised if there was an increase there."

"This data should reinforce your determination not to be exposed to secondhand smoke," Glynn said. "It can't be dismissed as something that is not harmful."

In related news, German researchers report that some children are born with a genetic defect that makes them more susceptible to the effects of passive smoke.

More than 3,000 children from two different German cities were examined for a study in the July 1 issue of Thorax. Some had a defect in glutathione S transferase (GST), an enzyme that helps the body clear the harmful effects of secondhand smoke.

Children with a GST defect and at least one smoking parent were five times more likely to have asthma, nearly five times as likely to experience wheezing, and nine times as likely to have shortness of breath.

More information

To learn more about secondhand smoke, visit the American Cancer Society.

SOURCES: Peter Whincup, professor, cardiovascular epidemiology, St. George's Hospital Medical School, London; Thomas Glynn, Ph.D., director, cancer science and trends, American Cancer Society, Washington D.C.; June 30, 2004,; July 1, 2004, Thorax
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