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Evidence suggests that light smoking (i.e., 1−5 cigarettes daily) increases risk for cardiovascular disease. In this meta-analysis of 141 prospective cohort studies, researchers quantified risk for coronary heart disease (CHD) and stroke associated with light smoking.
Men who smoked 1, 5, or 20 cigarettes daily had 48%, 58%, and 104% higher relative risks for CHD, respectively, than men who never smoked; for women, these higher relative risks were 57%, 76%, and 184%, respectively. In other words, smoking one or five cigarettes daily accounted for a substantial portion of the excess risk for CHD associated with smoking 20 cigarettes daily. Results were similar when analyses were adjusted for multiple potential confounders and for stroke.
Hackshaw A et al. Low cigarette consumption and risk of coronary heart disease and stroke: Meta-analysis of 141 cohort studies in 55 study reports. BMJ 2018 Jan 24; 360:j5855. (http://dx.doi.org/10.1136/bmj.j5855)
Johnson KC.Just one cigarette a day seriously elevates cardiovascular risk: Only total cessation will protect people and populations from tobacco's toxic legacy. BMJ 2018 Jan 24; 360:k167. (http://dx.doi.org/10.1136/bmj.k167)
Comment
In this study, smoking only one or five cigarettes daily was associated with excess risks for CHD and stroke. The possibility exists that some people who self-report smoking only a cigarette or two daily actually are heavier smokers. Nevertheless, the authors note that these results are biologically plausible, given that brief exposure to secondhand smoke and smoking even one cigarette have adverse cardiovascular effects (e.g., oxidative stress). Clinicians should advise light smokers, who believe it carries little or no risk, to stop smoking altogether.