Cigarettes Hurt Women's Hearts More than Men's

Women who smoke have a greater risk of developing coronary artery disease than men who smoke, a large systematic review and meta-analysis showed.

Compared with nonsmokers, women smokers have a 25% greater relative risk of coronary heart disease than do men who smoke, independent of other cardiovascular risk factors, reported Rachel R. Huxley, DPhil, from the University of Minnesota in Minneapolis, and Mark Woodward PhD, from Johns Hopkins University in Baltimore.

The relative risk increased by 2% for every additional year of study follow-up, which "lends support to the idea of a pathophysiological basis for the sex difference," according to the study published online in The Lancet.

"For example, women might extract a greater quantity of carcinogens and other toxic agents from the same number of cigarettes than men. This occurrence could explain why women who smoke have double the risk of lung cancer compared with their male counterparts," the researchers wrote.

"What makes the realization that women are at increased risk worrisome is that the tobacco industry views women as its growth market," wrote Matthew A. Steliga, MD, and Carolyn M. Dresler, MD, from the University of Arkansas in Little Rock, in an accompanying commentary.

And while there has been a reduction of smoking prevalence in men, "the rise or even stabilization of smoking in women will unfortunately result in substantial, preventable coronary heart disease morbidity and mortality."

Huxley and Woodward said that results from previous studies varied, which makes it difficult to establish "whether any reported sex differences between these studies is real or an artifact of methodological differences."

They therefore searched the literature and identified 26 articles (86 cohort studies) that included 3,912,809 individuals and 67,075 fatal and nonfatal coronary heart disease events.

In all, 39 cohorts were from Asia, 22 from the U.S., 16 from Europe, and nine from Australia, New Zealand, and the Pacific islands.

The dates of the studies ranged from 1966 to 2010, with a mean follow-up duration that spanned five to 40 years. Researchers divided their analyses into several groups depending upon study characteristics.

In one analysis of 2.4 million participants (75 cohort studies) that adjusted for cardiovascular risk factors other than coronary heart disease, the relative risk of developing coronary artery disease for women who smoked versus men who smoked was 1.25 for women (95% CI 1.12 to 1.39, P<0·0001).