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May 19, 1997

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AHA News Media Relations
(214) 706-1173 or 706-1396

NR 97-4531 (Circ/Kawachi)*

American Heart Association journal report:

Steady exposure to ìpassiveî smoke nearly doubles risk of heart attack, death for women, study shows

DALLAS, May 20 -- Constant exposure to second-hand smoke -- in the workplace or at home -- nearly doubles the risk of having a heart attack, a landmark study of more than 32,000 women suggests. Results of the research appear in todayís (May 20) American Heart Association journal Circulation.

Boston scientists say their 10-year investigation involving female nurses found a higher level of risk from passive smoking than has been seen before and provides the strongest evidence yet that exposure to smoke in the workplace is as dangerous as exposure at home.

Healthy, non-smoking nurses who said they were regularly exposed to ìpassiveî smoking by their co-workers or home companions had a 91 percent higher relative risk of a heart attack or death, compared to nurses who were not subjected to smoke, the researchers at Brigham and Womenís Hospital and Harvard Medical School report. For nurses who reported only occasional exposure to smoking in work or home environments, heart disease risk was 58 percent greater.

ìThose are larger risks than have been previously reported,î says Ichiro Kawachi, M.D., the studyís lead author. He and his co-workers expressed surprise over the magnitude of passive smoking-related heart disease risks that they found. In one major study published in Circulation last August, non-smoking spouses of smokers had about 20 percent higher heart disease death rates than non-smokers living with spouses who did not smoke.

Because heart disease is such a pervasive health problem, Kawachi asserts, the results of the nursesí study have major public policy implications for the nation.

The Environmental Protection Agency estimates that about 3,000 lung cancer deaths occur each year in the United States due to passive smoking, Kawachi points out. ìOnly a few cases of lung cancer occur among non-smokers,î he says.

ìSo if passive smoking causes heart disease, as our study suggests, then something like 10 to 20 times that number of deaths could occur from heart attack and passive smoking.î That would translate into between 30,000 and 60,000 deaths annually in the United States, he calculates. ìBecause heart disease is much more common [than lung cancer], even a small exposure to a relative risk can give rise to many more cases,î he says.

The finding of high risk associated with workplace smoke is a very important one, Kawachi

emphasizes. ìItís much harder to reduce smoking exposure at home, which can only be done through education. But we can always have smoke-free building policies. Itís exciting to be able to show that workplace exposure makes a difference.î

The EPA and other agencies have been reluctant to conclude that passive smoking is a cause of heart attacks, mainly because of a lack of conclusive studies and ìlingering concerns that those studies that have been done have not been controlled adequately for other lifestyle factors that might explain an increased risk,î says Kawachi, assistant professor at the Channing Laboratory at Brigham and Womenís Hospital and the Harvard School of Public Health.

ìBut our study addressed those issues,î he says. During the long follow-up of the Nurses Health Study participants, the scientists adjusted for ìa broad range of risk factorsî including high blood cholesterol and blood pressure, diet, exercise, diabetes and other conditions that could influence outcome. Although the women exposed to passive smoke did tend to be less healthy than those who werenít exposed, the adjustments for those potentially confounding factors resulted in only a ìmodestî reduction in smoking-related risk levels, the authors report.

When the study began in 1982, the nurses, who were age 36 to 61, gave information via questionnaires about the extent of their exposure to smoke at work and at home, including the number of years they had lived with a smoker. Of the 25,959 women who said they were exposed to passive smoking, 59 percent had occasional exposure at home or work, while 41 percent had regular exposure.

The researchers then carefully monitored the health of the women at two-year intervals. At the end of the study in 1992, there had been 152 cases of heart disease including 127 non-fatal and 25 fatal heart attacks among the 32,046 participants. Data on the number of cases were correlated with the information on smoke exposure to calculate levels of relative risk, i.e., the extra risk conferred by exposure to smoke compared to the heart disease risk experienced by those who were not so exposed.

The authors acknowledge limitations of their study, including the fact that exposure to passive smoking was assessed by self-report and only once, at the studyís outset. But Kawachi says that with societyís changes in the past decade, including more restrictive smoking rules in offices and public places, along with smoking cessation efforts, one would have expected to find a lower, not higher, trend of heart disease risk due to passive smoking. No such ìdownward driftî was seen, he says. Thus the studyís authors conclude:

ìThat regular exposure to passive smoking at home or work increases the risk of coronary heart disease among non-smoking women. The consistency of these findings with the existing totality of evidence increases the belief that the observed association represents cause and effect.î

Other co-authors of the study with Kawachi are: Graham A. Colditz, M.D.; Frank E. Speizer, M.D.; JoAnn E. Manson, M.D.; Meir J. Stampfer, M.D.; Walter C. Willett, M.D.; and Charles H. Hennekens, M.D.

Circulation is one of five journals published in Dallas by the American Heart Association. ### Media advisory: Dr.Kawachi can be reached in Boston by calling (617) 432-0235. Reporters may call (214) 706-1173 for copies of his report. (Please do not publish telephone numbers.)

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