Younger age explains why smokers more likely to survive heart attacks

A new study sheds light on the so-called “smokers’ paradox” -- the fact that a smoker is not only more likely than a nonsmoker to suffer a heart attack, but also more likely to survive it. The answer, research published in the February issue of Nicotine and Tobacco Research suggests, is mainly that the smoker is much younger at the time of the attack.

Previous studies have established that smokers with acute heart attacks are younger than nonsmokers, tend to have fewer illnesses and exhibit fewer cardiac risk factors. However, past researchers have not been able to agree on how much these differences account for the lower mortality from heart attacks among smokers.

The current study attempts to confirm and finally explain the smokers’ paradox by examining the largest group of heart attack patients to date, more than seven times the size of the largest previously studied group.

More than a quarter million cases included in the second National Registry of Myocardial Infarction during a three-year period were analyzed. Of the 297,458 patients included, 24 percent were smoking at the time of their heart attack, while 76 percent had either quit smoking or had never smoked.

Analysis of patient data revealed that smokers are only half as likely as nonsmokers to die while hospitalized for their attacks. In addition the smokers were, on the average, 14 years younger at the time of the attack -- an observation that “confirmed the strong association of smoking and premature age," reports lead author Steven G. Gourlay, Ph.D., of Genentech Inc. and the University of California at San Francisco.

The researchers observed other differences between the two groups, including a lower incidence of disease associated with high cardiac risk, such as diabetes or angina, among the smokers, and differences in the types of heart attacks suffered.

Gourlay and his associates found that the age difference between smokers and non-smokers accounts for almost all the observed difference in mortality rates. Thus, smokers primarily have their relative youth to thank for their improved short-term chances of survival.

The small remaining “association of smoking and better prognosis was not explained by [any of the other variables examined] and its cause remains unclear,” Gourlay concludes.

The National Registry of Myocardial Infarction 2 and the current research are supported by Genentech, Inc.

Nicotine & Tobacco Research is the official peer-reviewed quarterly journal of the Society for Research on Nicotine and Tobacco. For information about the journal, contact Gary E. Swan, Ph.D., at (650) 859-5322.

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