Women who smoke have a higher risk of developing coronary heart disease than men, a large international study finds. 
 
 The study published online in the Lancet Thursday, collected data on more than two million people and concluded that the increased risk of heart disease tied to smoking was 1.25 times higher for women. 
 
 The longer a women smoked, the greater her heart disease risk compared with a man who smoked for the same time period, researchers said. 
 
 The lead authors were Dr. Rachel Huxley, from the University of Minnesota and Dr. Mark Woodward, from Johns Hopkins University in Baltimore, Md. They received no funding for their research. 
 
 The finding that among smokers, the excess risk of heart disease in women compared with men increases by two per cent for every year lends support to the possibility that physiological differences between men and women make a difference, the researchers said. 
 
 For example, women might receive more carcinogens or toxins from smoking the same number of cigarettes than men, the investigators speculated. 
 
 "Whether mechanisms underlying the sex difference in risk of coronary heart disease are biological or related to differences in smoking behaviour between men and women is unclear," the study's authors concluded. 
 
 "Tobacco-control programs should consider women, particularly in those countries where smoking among young women is increasing in prevalence. 
 
 The study was large and examined a diverse range of populations worldwide, with consistent findings, Huxley and Woodward said. 
 
 They also acknowledged limitations of the research, such as an inability to take use of birth control pills into account in the analysis. Studies also defined non-smokers differently, with some including those who had never smoked and others defining them as not-current smokers. 
 
 Tobacco companies targeting women 
 
 In most societies, smoking rates are higher for men than for women, but more men than women are quitting, wrote Dr. Carolyn Dresler journal in a commentary that accompanies the research paper. 
 
 "What makes the realization that women are at increased risk worrisome is that the tobacco industry views women as its growth market," said Dresler of the Tobacco Prevention and Cessation Program at the Arkansas Department of Health, in Little Rock. 
 
 Tobacco companies are increasingly targeting women with slim brands and slick packaging, said Ellen Mason, senior cardiac nurse at the British Heart Foundation. 
 
 Mason suggested introducing plain packaging to increase the effectiveness of health warnings and to reduce the appeal of tobacco products. 
 
 Think of quitting 
 
 In 2010, about one in five women in Canada smoked, according to Health Canada. Among female smokers in 2002, less than half indicated that they were even considering quitting. 
 
 After quitting for one year, the risk of coronary heart disease drops by about half, and quitting has many other health benefits, said CBC medical specialist Dr. Karl Kabasele, a public health physician in Toronto. 
 
 Even if a woman is thinking of quitting, Kabasele suggested she talk to her doctor about the many tools and support groups that are now available. Many are covered by provincial health plans. 

 This article is a collaboration between MedPage Today® and: 
 
 Action Points Note that a large meta-analysis indicates a higher relative risk of coronary heart disease for women smokers, with an additional increase in the female-to-male relative risk ratio for every additional year of smoking. 
 
 
 
 Point out that the underlying mechanisms by which smoking might be more hazardous in female smokers are unclear, but the authors suggest one possibility is that women might extract a greater quantity of toxic agents from cigarettes than men. 
 
 
 
 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). 
 
 After adjustment for potential publication bias, the result remained unchanged. 
 
 Another group of 54 cohort studies (3.3 million individuals) reported age-adjusted relative risk estimates for fatal and non-fatal coronary heart disease associated with smoking. The risk was greater for women than men (1.11, 95% CI 0.99 to 1.26, P=0·06). 
 
 Adjustment for potential publication bias had little effect: 1.10, 95% CI 0.99 to 1.24, P=0·08. 
 
 Researchers examined the risk in relation to various age groups, from 30 to 80 years or older. Except for those between 30 and 44 years, women in all other age groups had a greater risk of coronary heart disease then men. The difference became significant in those between 60 and 69 years. 
 
 Men who quit smoking also fared better than women who quit. 
 
 Researchers pooled 13 articles (53 cohort studies) involving ex-smokers and never-smokers. Eight studies showed a relative risk below unity, "suggesting an increased beneficial effect of smoking cessation in men compared with women." 
 
 The remaining seven studies did not indicate a difference between men and women on subsequent risk of coronary heart disease after quitting smoking (RR 0.96, 95% CI 0.86 to 1.08, P=0·53). 
 
 "Although more men than women smoke, those women who do smoke have a greater risk of coronary heart disease and therefore targeting of both sexes is imperative for smoking prevention and cessation on a global, national, and individual basis," wrote Steliga and Dresler in their commentary. 
 
 The study is limited by its lack of standardization for dose and duration of smoking, inability to adjust for oral contraceptive use, and the various definitions of "non-smokers" used in the studies. 
 
 From the American Heart Association: 
 
 The authors reported no funding for the study, as well as no conflicts of interest. The editorialists declared they had no conflicts of interest.
– Scientists have issued a warning for women smokers: Their relative risk of coronary heart disease is 25% higher than that of male smokers, a review of studies from 1966 to 2010 reveals. The reason is unclear, but "women might extract a greater quantity of carcinogens and other toxic agents from the same number of cigarettes than men,” wrote the researchers in the Lancet. That “could explain why women who smoke have double the risk of lung cancer compared with their male counterparts." The study examined data on more than 2 million people around the world, notes the CBC. “What makes the realization that women are at increased risk worrisome is that the tobacco industry views women as its growth market,” wrote two doctors in an accompanying commentary, according to MedPage Today. So while smoking rates are generally higher for men, the "targeting of both sexes is imperative for smoking prevention and cessation on a global, national, and individual basis.”