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Passive smoking may increase the risk of coronary heart disease, but not stroke
(May 2005)

Most studies of the effects of passive smoking are based on occurrence of heart attacks or cancer among men or women who did not smoke, but had smoking spouses or partners. This new study of 2,105 non-smoking men in 18 towns in England, Wales, and Scotland has a major advantage in that risk was related to blood cotinine levels, a valid measurement of nicotine exposure. The men were enrolled in 1978-1980 and followed for 20 years. During that followup period, those men, average age 50 years, who were exposed to smokers had about a 50 percent increased risk of fatal or non-fatal heart attacks. Interestingly, when the followup was divided into five-year periods, the risk of heart attack was greatest in the first five-year period, with almost a fourfold increased risk; that fell to a twofold increase in the second five-year period; thereafter, there was no increased risk. There was no evidence that passive smoking increased the risk of stroke

Non-smokers were compared in the analysis with a group of men who were active smokers of one to nine cigarettes a day, whose cotinine levels in the blood were ten times the maximum found in the non-smokers (the passive smokers). There was only a very modest increase in heart attack risk among the active smokers compared to the passive smokers, far less than would be expected considering the huge differences in blood cotinine levels.

Commentary: The authors argue that their findings reflect overall exposure at home, in the community, and at work, and that explains the finding of even greater risk of heart attack than found in other studies when only exposure from a partner in the home was studied; in those studies, risk was, in general, increased by about 25 to 30 percent. The explanation for the finding that the increased risk was only found in the first ten years of exposure is not entirely satisfactory; the authors suggest it is related to the decreased frequency over time of active smoking and increasing regulations that protect the public from passive smoking in the community and at work. That may or may not be so. Still, the increased risk during the first five years (almost fourfold) is quite impressive.

The negative findings in regard to stroke tend to refute some previous claims.

It would have been nice if cotinine levels had also been measured during the followup period, as well as at enrollment. The finding of only a very modest increased risk of heart attack among active moderate smokers compared to non-smokers is a bit surprising and makes it imperative not to over-interpret this study.

Ratings:

or 

for some increase in risk for heart attack among passive smokers

for any claim that passive smoking increases the risk of stroke

Whincup, P.H., et al. Passive smoking and risk of coronary heart disease and stroke. British Medical Journal. Vol 329 (July) Pgs 200-205. 2004.

Smoking cigarettes does nobody any good and can cause a lot of harm. The extent of risk from passive smoking in regard to heart attacks and cancer is still not completely clear. As of 2005, the best statement, based on the various studies, is that passive smoking for a substantial time period results in a small increased risk of heart attack and a very small increased risk of lung cancer - Ed.

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