Environmental Tobacco Smoke and Coronary Heart Disease Mortality in the United States—A Meta-Analysis and Critique

Abstract

Several major meta-analyses have concluded that exposure to environmental tobacco smoke (ETS) increases the risk of coronary heart disease (CHD) by about 25% among never smokers. However, these reviews have excluded a large portion of the epidemiologic evidence on questionable grounds and have been inconsistent in the selection of the results that are included. We conducted an updated meta-analysis and critique of the evidence on ETS exposure and its relationship to death from CHD among never smokers. Our focus is on the U.S. cohort studies, which provide the vast majority of the available evidence. ETS exposure is assessed in terms of spousal smoking, self-reported estimates, and personal monitoring. The epidemiologic results are summarized by means of overall relative risks and dose-response relationships. The methodological issues of publication bias, exposure misclassification, and confounding are discussed. Several large studies indicate that spousal smoking history is a valid measure of relative exposure to ETS, particularly for females. Personal monitoring of nonsmokers indicates that their average ETS exposure from a smoking spouse is equivalent in terms of nicotine exposure to smoking less than 0.1 cigarettes per day. When all relevant studies are included in the meta-analysis and results are appropriately combined, current or ever exposure to ETS, as approximated by spousal smoking, is associated with roughly a 5% increased risk of death from CHD in never smokers. Furthermore, there is no dose-response relationship and no elevated risk associated with the highest level of ETS exposure in males or females. An objective assessment of the available epidemiologic evidence indicates that the association of ETS with CHD death in U.S. never smokers is very weak. Previous assessments appear to have overestimated the strength of the association.

An Assessment of Air Pollution Exposure Information for Health Studies

“…Adverse effects of ETS have been reported in epidemiological studies [25,26]. However, I found no air pollution studies that accounted for ETS increments to PM exposures.…”

Tobacco Industry Efforts Undermining Evidence Linking Secondhand Smoke With Cardiovascular Disease

“…Tobacco industry-funded epidemiological analyses 57,58,73 of large data sets were used to argue against an epidemiological association between SHS and CVD, but these analyses all suffered from exposure misclassification problems that eventually even some in the tobacco industry 71 recognized. More recent industry-funded publications 68,75 report an increased risk of CVD associated with SHS but claim that the magnitude of the risk is far below the generally accepted 30% increase. 7,8 When early tobacco industry-funded work demonstrated that SHS increased atherosclerosis, 39,45,46 the industry criticized the findings for using smoke concentrations larger than that in the real world and withdrew funding.…”

“…The authors 75 acknowledged that the non-US studies tended to report higher risks but have 1 sentence stating that inclusion of the non-US studies did not "materially alter" the summary relative risks for the US results, even though their results differed from the risk estimates produced by non-tobaccofunded sources by a factor of 6.…”

“…103 The same journal also published the 2006 PM-funded epidemiological meta-analysis of SHS and cardiovascular mortality. 75 ) Smith and colleagues 85 concluded that SHS exposure levels did not activate platelets in "typical home environments" because no difference in urinary thromboxane and prostacyclin was observed between nonsmokers from nonsmoking homes and nonsmokers from smoking homes. However, Smith's smoker "control group" did not demonstrate significantly elevated thromboxane relative to the 2 nonsmoker groups, which contradicted previous tobacco industry-funded literature 94,95 demonstrating that active smoking was associated with thromboxane release.…”

Kritiker sind keine „Leugner“

“…Die Autoren kommen zu dem Ergebnis: "It seems premature to conclude that environmental tobacco smoke causes death from coronary heart disease and lung cancer" [9]. Fünf Jahre später bekräftigen dieselben Autoren ihre Vorbehalte in einer Metaanalyse etlicher Untersuchungen über das Risiko von Herz-Kreislauf-Erkrankungen [10]. 2009 werden in einem Buch zur Geschichte der Tabakbekämpfung 64 Untersuchungen aufgelistet, von denen 55 keinen statistischen Beleg für angebliche Gefahren des "Passivrauchens" beibringen können [11].…”