TOPICS > Health

Danger: Second-Hand Smoke

May 20, 1997 at 12:00 AM EDT


CHARLES KRAUSE: For years scientists published data showing a direct link between cigarette smoking and heart disease. But does second-hand cigarette smoke also cause heart disease. New research published in today’s issue of the journal Circulation strongly suggests that it does. Here to tell us about the link between second-hand smoke inhaled even by non-smokers and heart attacks is Dr. Ichiro Kawachi of the Harvard School of Public Health, the lead author of the new study published today.

Dr. Kawachi, welcome.

DR. ICHIRO KAWACHI, Harvard School of Public Health: Good evening.

CHARLES KRAUSE: What are the principal findings of your study?

DR. ICHIRO KAWACHI: We followed a group of about 32,000 women over a period of 10 years to see whether passive smoking might increase the risk of heart attack. And basically we found that women who are regularly exposed in either the work or the home are at about double the risk for heart attack compared to those who are not exposed.

CHARLES KRAUSE: How did you find these women, and how did you monitor them?

DR. ICHIRO KAWACHI: Basically, we took advantage of a 20-year-long ongoing study of women, and about halfway through the study, we sent out a questionnaire asking them whether they were exposed to passive smoking in the home and in the workplace, and then we just sat and waited and saw what happened to them in terms of their heart attack rates.

CHARLES KRAUSE: Now how do your findings advance knowledge of the impact of second-hand smoke?

DR. ICHIRO KAWACHI: Well, there have been previous studies passing smoking and heart attack, but there have been two criticisms leveled at studies that have been done in the past. One is that they haven’t asked about exposure in the workplace, and the second is that most studies have not adequately managed to take account of the whole range of other things that might otherwise explain the association. And we were able to address both of these weaknesses in our study.

CHARLES KRAUSE: For example, what other kinds of things might affect heart attack?

DR. ICHIRO KAWACHI: Well, aside from exposure to passive smoking, we asked about their diet, their fat intake, their exercise levels, family history of heart attack, whether they had high blood pressure or high cholesterol, their body weight and so on and so forth. And after taking account of all of these differences and comparing like woman with like, the only difference being that one group was exposed to passive smoking while the other was not, we still found that women exposed to passive smoking were at about twice the risk of heart attack.

CHARLES KRAUSE: Explain for us, if you would, the connection, or the medical connection between this passive smoke and heart attacks.

DR. ICHIRO KAWACHI: It used to be said when I was in medical school that if you can understand the effects of tobacco smoke on the cardiovascular system, you pretty much understand the whole cardiovascular system because the cocktail of chemicals, about 2,000 chemicals in tobacco smoke, initially does everything to the cardiovascular system. It directly damages the lining of the lining of the arteries.

It reduces the capacity of the blood to carry oxygen to the tissues. It increases the stickiness of the blood, and so on and so forth, so we’re saying that virtually everything that we know active smoking does to the circulatory system probably the same thing is happening to the bodies of people who inhale second-hand smoke.

CHARLES KRAUSE: Does your study–did you have any way of determining how long one would have to–how much second-hand smoke one would have to be exposed to, to have it be harmful to you?

DR. ICHIRO KAWACHI: That’s actually the one question that I think needs to be looked at in more refined studies. We weren’t able to precisely estimate just how much of a dose and how long one would have to be exposed to in order to get into increased–situations of increased risk, such as we observed. I think it’s safe to say that knowing what is in tobacco smoke, any exposure is likely to constitute some measurable degree of risk. In other words, there are no known stage thresholds of exposure for most of the chemicals that we know are harmful in tobacco smoke.

CHARLES KRAUSE: Let me ask you a couple of questions about the methodology. Only women were involved in your study. Would the impact of second-hand smoke apply to men as well?

DR. ICHIRO KAWACHI: We see no reason why it wouldn’t. The risks of heart attack among active smokers are pretty similar comparing men to women, and there have been previous studies that–of passive smoking and heart attack that did include men. And although they weren’t able to control it for quite the range of things that we were able to, there’s no reason to believe that the risks among men would be any different.

CHARLES KRAUSE: Now, another question is, as I understand it, the women involved in your study reported, in effect, on themselves, they answered questionnaires every so often, is that correct?

DR. ICHIRO KAWACHI: Yes. In fact, they answered the question about passive smoking at the beginning of the study in 1982, and their exposure status was self-reported. In other words, we believed them when they said that they were exposed to second-hand smoke. The thing that should be noted about that particular designed feature is that both of these things are likely to underestimate the true association between passive smoking and heart attack because since 1982, when the study began, Americans have been becoming less and less exposed in general because of rising standards of restrictions of exposure in workplaces. And that kind of things is, if anything, likely to underestimate the truth of smoking, passive smoking.

CHARLES KRAUSE: But at the same time, if you only asked them once and if you relied on their answers, I mean, isn’t there the possibility that perhaps they were inaccurate or unreliable in some way that could affect the outcome of your findings?

DR. ICHIRO KAWACHI: I think most studies in the past which have done very careful measurements of saliva and urine to see whether people are really exposed when they said they were have found that people, in fact, vastly underestimate the amount of exposure. In other words, people are much more exposed to passive smoking than they think they are. And, again, that’s a kind of a bias in the conservative direction. In other words, if you studied people as being not exposed when, in fact, they are, that’s likely to result from the underestimate of the true association between passive smoking and disease.

CHARLES KRAUSE: Now you were quoted in the New York Times today as saying that if you extrapolated your findings, that as many as 50,000 Americans every year would have heart attacks because of second-hand smoke. How did you arrive at that figure?

DR. ICHIRO KAWACHI: Actually, they weren’t arrived at by us but by independent researchers who published those estimates a couple of years ago. The surgeon general has estimated that approximately 3,000 Americans die each year from passive smoking, causing lung cancer. And these other researchers, Kyle Steinland and A.J. Wellslyn among them, have estimated that if the association between passive smoking and heart attack is true, then up to 10 times as many Americans would die from heart attack. That is about 30,000 Americans each year.

CHARLES KRAUSE: Well, Dr. Kawachi, we’ll have to leave it there, but I thank you very much for joining us. Thank you.