Thursday, February 3, 2005

Secondhand Smoke Increases Women’s Risk of Dying from Heart Disease
By Julie McKeel

The DCRI’s Dr. Rowena Dolor, along with colleagues from the Durham Veterans Affairs Medical Center and Duke University Medical Center have found that nonsmoking women’s exposure to secondhand (passive) smoke increases their risk of dying from heart disease by 15% compared with nonsmoking women not exposed to passive smoke.

Their results were published in the October 2004 issue of the Journal of Women’s Health. The nine studies they selected for meta-analysis used cardiac death as an endpoint. The study populations varied in size from 513 to 208,372 participants, with follow-up periods ranging from 6 to 39 years. Two of the studies were performed outside the United States.

The study analysis found an increased risk of cardiac death in women exposed to passive smoke despite the inclusion of the most recently published and controversial study, which showed no difference in cardiac death in women exposed and unexposed to secondhand smoke.

The National Research Council defines secondhand smoke exposure as being equivalent to actively smoking 0.1–1.0 cigarettes per day, based on measurements of urine cotinine (a nicotine byproduct). The controversy focuses on how a nonsmokers’ risk of fatal coronary artery disease (CAD) can be 20%–30% higher than that of an active smoker who smokes one cigarette a day. Other studies established that the excess risk associated with exposure to passive smoke (or, by definition, smoking one cigarette a day) is much greater than 1% of the risk from smoking 20 cigarettes per day.

Passive smoke consists of sidestream smoke (smoke that comes from the end of a burning cigarette) and smoke exhaled by the smoker (mainstream smoke). Most of the smoke in a room comes from sidestream smoke, and many toxins, including carbon monoxide, are much more concentrated in sidestream smoke than in mainstream smoke. Since carbon monoxide can aggravate chest pain (angina), this higher concentration of toxins in sidestream smoke is believed to be one reason why a nonsmoker’s exposure to passive smoke can lead to fatal CAD.

In addition to the increased risk of CAD death in women exposed to secondhand smoke, other studies have confirmed that nonsmoking women exposed to passive smoke are also at increased risk for lung cancer. Pregnant nonsmoking women exposed to passive smoke have given birth to lower-weight infants. A slightly increased risk for intrauterine growth retardation was noted as well.

In March 2001, the U.S. Surgeon General released a report on women and smoking.¹ The report identifies cigarette smoking as the leading cause of preventable death in the United States. Since 1980, 3 million women have died prematurely from smoking-related tumors, CAD, and other related diseases. The Surgeon General’s report also highlights the risk of exposure to secondhand smoke. Passive exposure is the third leading cause of preventable death in this country, resulting in over 50,000 deaths each year.

Following the lead of the American Heart Association (AHA), as presented in the AHA’s guidelines for prevention of CAD in women, the current study’s authors recommend counseling women on reducing or avoiding exposure to secondhand smoke.

Funding for this study was provided by the AHA, the National Cancer Institute, and Women’s Health Fellowship, Department of Veterans Affairs.