'Light' Cigarettes Take Heavy Toll on Coronaries

KONYA, Turkey, May 15 -- So-called light cigarettes are no less harmful to cardiovascular circulation that the regular kind, researchers here documented.

Smoking either two regular cigarettes or two billed as low-tar, low-nicotine within 15 minutes caused rapid and significant decreases in coronary flow velocity reserve, an indicator of microvascular function, found Hakan Gullu, M.D., and colleagues of Baskent University and Konya Teaching and Medical Research Center.

"Smoking low-tar, low-nicotine cigarettes impairs the coronary flow velocity reserve as severely as smoking regular cigarettes," they reported online in Heart, a BMJ specialty journal. "Coronary flow velocity reserve values are similar in light cigarette and regular cigarette smokers and significantly lower than in controls."

Both nicotine and carbon monoxide, two of the most prominent of the 2,000 or so toxic components of cigarette smoke, exert a baleful influence on vascular endothelial function, particularly in the coronary vasculature, the authors noted.

"Nicotine causes increased endothelial cell proliferation and intimal hyperplasia, and increased serum carbon monoxide levels have been shown to cause increased endothelial cells circulating in human blood," they wrote.

"Smaller amounts of nicotine than that found in cigarette smoke can cause acute endothelial dysfunction. Free radicals contained in the cigarette smoke tar can damage the vascular endothelium. It is known that the adverse effect on the endothelial functions is the same whether a small or large number of cigarettes is smoked a day."

Working under the assumption that cigarettes low in tar and nicotine might therefore be kinder and gentler to the arteries of smokers, the authors enrolled 40 smokers in their mid-20s and 22 healthy non-smoking controls of a similar age.

Half the smokers customarily smoked regular cigarettes, containing 12 mg of tar, 0.9 mg of nicotine, and 12 mg carbon monoxide, and half smoked light cigarettes, each of which delivers 8 mg of tar, 0.6 mg of nicotine, and 9 mg of carbon monoxide.

After a 12-hour, smoke-free fast, the participants all underwent echocardiography, including coronary flow velocity reserve measurement. Two days later, the smokers then smoked two of their usual cigarettes within 15 minutes, and within half an hour of completing the second cigarette underwent a second ECG exam with coronary flow velocity reserve measurement.

The authors found that mean coronary flow velocity reserve values were similar between the two smoker groups, and significantly lower than in the controls, at 2.68 (standard deviation 0.50) for light smokers, 2.65 (SD 0.61), for regular smokers, and 3.11 (SD 0.53) for non-smokers (P=0.013).

A paired t test performed both before and after smoking showed that smoking two light cigarettes acutely decreased the coronary flow velocity reserve from 2.68 (SD 0.50) to 2.05 (SD 0.43) (P=0.001), and smoking two regular cigarettes acutely decreased coronary flow velocity reserve from 2.65 (SD 0.61) to 2.18 (SD 0.48) (P=0.001).

"Our study suggests that reducing the nicotine and tar yield is not sufficient for a cigarette to be called less hazardous, and other noxious compounds in cigarettes continue to compromise human health," the authors wrote. "Smoking low-tar, low-nicotine cigarettes seems to have the same unfavorable effect on the coronary microvascular functions as smoking regular cigarettes. Action should be taken to prohibit misleading terminology such as 'light'."