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    Secondhand Smoke Hurts the Heart

    Even Low Exposures Make Big Impact
    WebMD Health News
    Reviewed by Louise Chang, MD

    Feb. 12, 2007 -- There is new evidence directly linking exposure to secondhand smoke with an increased risk for heart disease.

    Even low-level indirect exposure to cigarette smoke was associated with a significant rise in heart disease risk in the research conducted by researchers from the U.K.'s University of Nottingham.

    The study is the first to directly measure secondhand smoke exposure through levels of a nicotine byproduct in the blood. Previous studies have relied on participants' recall of exposure.

    Compared with people in the study with no detectable exposures to nicotine, those with low- and high exposure levels also had significantly higher levels of two important markers of heart disease risk.

    "These findings suggest that secondhand smoke exposure has a clinically important effect on susceptibility to heart disease, even at relatively low levels of exposure, and they highlight the importance of minimizing the public's exposure to secondhand smoke," researcher Andrea Venn, PhD, tells WebMD.

    A Known Risk Factor

    Smoking is a well-established risk factor for cardiovascular disease. Past research shows that the risk associated with secondhand smoke exposure is about a third of that seen in active smokers.

    In an effort to further clarify this risk, Venn and colleague John Britton, MD, examined established blood biomarkers of cigarette smoke exposure and heart disease risk in 7,599 adults who had never smoked. The participants were enrolled in the Third National Health and Nutrition Examination Survey (NHANES III), conducted in the United States.

    Sixty-eight percent of those evaluated were women, and the median age of the study participants was 38.

    Blood sample analysis included measurements of cotinine, the nicotine byproduct used to measure nicotine exposure.

    The researchers also examined whether nicotine exposure was associated with markers of increased heart disease risk. They did this by measuring blood levels of four markers of disease -- C-reactive protein, white blood cell count, fibrinogen, and homocysteine.

    Slightly less than one out of five study participants had no detectable cotinine in their blood samples, while the rest had low or high levels.

    Eighteen percent of those with low blood levels of cotinine and 56% of those with high cotinine levels reported living with a smoker or being exposed to tobacco smoke at work.

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