Approximately 40 percent of all deaths in Western countries are attributed to ischemic heart disease. Within the past 20 to 30 years, smoking has become more prevalent in women, and their smoking patterns have changed to more closely resemble those of men. Changes in the prevalence and patterns of smoking in women could have a dramatic impact on mortality rates. Prescott and colleagues conducted a large, population-based study in Denmark to compare the risk of myocardial infarction associated with smoking in men and women.
The authors pooled data from three large studies to obtain a cohort of 11,472 women and 13,191 men. These study participants were followed for a mean of 12.3 years. Risk factors for cardiovascular disease were assessed by using a self-administered questionnaire and laboratory tests. The type of tobacco smoked was recorded, and the patient's duration of smoking was measured. Alcohol consumption was classified according to total weekly intake. National hospital data systems and mortality registers were used to monitor hospital admissions for fatal and nonfatal myocardial infarctions.
During the follow-up period, 512 women and 1,251 men had myocardial infarctions. A total of 104 women and 274 men died as a result. The risk of myocardial infarction was strongly associated with elevated systolic blood pressure, body mass index, height, unfavorable lipoprotein profiles, education, diabetes, alcohol intake and physical inactivity during leisure time. Men had higher incidence rates of myocardial infarction than did women at all ages. The relative risk of myocardial infarction increased with tobacco use in both men and women. The relative risk of myocardial infarction in women who were current smokers was 2.24 compared with 1.43 in male smokers. This difference was significant and was unchanged after adjustment for other risk factors. Risks in ex-smokers were not increased, but in current smokers there was a clear dose-response relationship. Women were found to have a higher relative risk in each category. The risk increased with age and in smokers of both sexes who inhaled.
The authors conclude that the relative risk of myocardial infarction in women who smoke is approximately 50 percent greater than the risk in male smokers. This difference persisted after adjustment for multiple cardiovascular risk factors. The authors suggest that a possible cause may be the interaction of some hormonal factors with components of the inhaled smoke. There is growing epidemiologic evidence that women who smoke are relatively deficient in estrogen. Hormone replacement therapy may mitigate the risk of stroke to some extent, but clinical trials have not yet addressed this issue.
editor's note: This study makes depressing reading, especially as it verifies what was suspected from earlier, smaller studies and clinical observations. Women do appear to be more vulnerable to the adverse cardiovascular effects of cigarette smoking than men. An onslaught of cardiovascular disease in women around menopause or even at younger ages has been anticipated (and appears to be happening) based purely on the increase in smoking and the change to more “male” patterns of smoking, such as completely smoking each cigarette and inhaling. We can now expect this epidemic to be exaggerated because of biologic vulnerability. Chronic obstructive pulmonary disease is now more common in women than in men. Must we simply document the gradual “feminization” of many smoking-related diseases? If every physician inquired about smoking cessation in every female patient at every visit, we would at least make a start toward reversing this trend.—a.d.w.