An Article published Online First by The Lancet shows that the increased risk of developing coronary heart disease conferred by smoking is 25% higher for women compared with men. This increased risk for women could, suggest the authors, be due to physiological differences between the sexes, with cigarette smoke toxins possibly having a more potent effect on women. The Article is by Dr Rachel R Huxley, Division of Epidemiology, University of Minnesota, Minneapolis, MN, USA, and Dr Mark Woodward, Johns Hopkins University, Baltimore, MD, USA.
The authors' meta-analysis included around 4 million individuals and 67000 coronary heart disease events from 86 studies. They found that in 75 cohorts (total 2•4 million participants) that adjusted for cardiovascular risk factors other than coronary heart disease, the pooled adjusted female-to-male relative risk ratio (RRR) of smoking compared with not smoking for coronary heart disease was 1•25 (ie, 25% higher for women). This RRR increased by 2% for every additional year of follow-up, meaning that the longer a woman smokes, the higher her risk of developing CHD becomes compared with a man who has smoked the same length of time.
The authors say: "Cigarette smoking is one of the main causes of coronary heart disease worldwide and will remain so as populations that have so far been relatively unscathed by the smoking epidemic begin to smoke to a degree previously noted only in high-income countries. This expectation is especially true for young women in whom the popularity of smoking, particularly in some low-income and middle-income countries, might be on the rise."
The actual RRR could, say the authors, be even higher. Women, on average, smoke fewer cigarettes per day than men, and in many countries the smoking epidemic in women has been much shorter in duration for women—both these factors mean that the RRR could actually be even higher for women.
The authors say: "The finding that, among smokers, the excess risk of coronary heart disease in women compared with men increases by 2% for every extra year of study follow-up lends support to the idea of a pathophysiological basis for the sex difference. 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."
They conclude: "Physicians and health professionals should be encouraged to increase their efforts at promotion of smoking cessation in all individuals. Present trends in female smoking, and this report, suggest that inclusion of a female perspective in tobacco-control policies is crucial."
In a linked Comment, Dr Matthew A Steliga, University of Arkansas for Medical Sciences, Little Rock, AR, USA, and Dr Carolyn M Dresler, Tobacco Prevention and Cessation Program, Arkansas Department of Health, Little Rock, AR, USA, say: "What makes the realisation that women are at increased risk worrisome is that the tobacco industry views women as its growth market."
They conclude: "National and international organisations such as the International Network of Women Against Tobacco and the WHO's Tobacco Free Initiative are important reference organisations to promote more effective tobacco cessation in women. Although more men than women smoke, those women who smoke do have a greater risk for having coronary heart disease and therefore targeting of both sexes is imperative for smoking prevention and cessation on a global, national, and individual basis."
Dr Rachel R Huxley, Division of Epidemiology, University of Minnesota, Minneapolis, MN, USA. T) +1 952 250 1730 E) rachux@gmail.com
Dr Carolyn M Dresler, Tobacco Prevention and Cessation Program, Arkansas Department of Health, Little Rock, AR, USA. T) +1 501 661 2797 E) carolyn_dresler@ksg03.harvard.edu
Journal
The Lancet