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THE NEW ENGLAND JOURNAL Ol- MtDlClNt 



June 15, mU'J 



these elements (but not carbon monoxide or other gas- 

 eous components) trom tobacco smoke. More recent 

 engineering refinements to decrease tar and nicotine 

 yields include the use of reconstituted sheet tobacco 

 containing larger amounts of stems, which has less 

 nicotine; expanded or puffed tobacco, which results in 

 less tobacco per cigarette; faster burning limes, more 

 porous [>aper, and longer filter overwraps, which 

 cause the smoking machine to take fewer pufl°s per 

 cigarette; and ventilated filters that allow dilution 

 of the tobacco smoke with air. It is important to recog- 

 nize that modem low-yield cigarettes contain the same 

 type of tobacco and the same amount of nicotine 

 by weight as higher-yield cigarettes.' Thus, the low- 

 yield cigarette is not low in yield because it contsiins 

 less of anything, but because it is engineered to make 

 less smoke available to the smoker (or at least to the 

 smoking machine). 



However, people do not smoke the way machines 

 do. Most smokers are addicted to nicotine; they 

 tend to compensate for their lower-yield cigarettes by 

 smoking them in such a way as to optimize the intake 

 of nicotine.* By taking more frequent pufis, inhaling 

 more deeply, occluding the ventilation holes with lips 

 or fingers, and smoking more cigarettes, people take in 

 considerably more tar, nicotine, and carbon mono.xide 

 than would be predicted by smoking machines. Stud- 

 ies of people who smoked their own selected brands of 

 higher- or lower-yield cigarettes indicate similar or 

 only slightly lower levels of cotininc (a metabolite of 

 nicotine commonly used as a marker of nicotine in- 

 take) or carbon monoxide in smokers of all but possi- 

 bly the lowest-yield cigarette (I mg of tar).''** De- 

 spite a great deal of promodon and advertising, 

 very-low-yield cigarettes ( 1 to 3 mg of tar) are not very 

 popular and account for only a small percentage of 

 sales,' presumably because most smokers do not ob- 

 tain enough nicotine to find them satisfying. In gener- 

 al, low-yield cigarettes do have a lower ratio of tar to 

 nicotine yield as tested by smoking machines, which 

 has sugge:ited that even if smokers compensate for 

 nicotine, their avposure to tar will be reduced.^ Unfor- 

 tunately, inteiuively smoking low-yield cigarettes in- 

 creases the tar-to-nicotine ratio and reduces or even 

 negates any possible benefit of selective diflerences 

 in yield.* 



Epidemiologic data indicate that low-yield ciga- 

 rettes are less hazardous than high-yield cigarettes 

 with respect to lung, laryngeal, esophageal, and other 

 cancers and possibly chrotiic obstructive lung dis- 

 ease."*"'^ However, it is important to recognize that 

 the definition of "low yield" has changed over the 

 years. A tow-yidd cigarette in the 1960s (18 mg of tar 

 or less) would be a high-yield cigarette today. Many of 

 the older dguette* were unfiltered. Not only was their 

 yield of tar much greater, but the tar was also qualiu- 

 dvely more toxic than that in modem cigarettes. As is 

 appropriate when one is studying diseases that may 

 take 20 years or longer to develop, most epidemiologic 

 studies of cancer and lung disease have used the older 

 cigarettes in their comparisons. Studies indicate that 



the risk of lung cancer is reduced substantially (by 20 

 to 40 percent) in smokers of the old-style low-yield as 

 compared with the old-style high-yield cigarettes; 

 however, that risk is still markedly higher than the 

 risk in nonsmokers."*"" Similar results have recently 

 been reported for laryngeal, esophageal, and other 

 cancers." The data on chronic lung disease arc less 

 clear. Some studies suggest a reduction in cough and 

 phlegm, fewer deaths due to emphysema, or slightly 

 less seriously impaired pulmonary function in smokers 

 of filtered as compared with unfiltered cigarettes.'"" 

 Other studies find no difference in lung function as 

 related to cigarette yield." It is noteworthy that [he 

 greatest reduction in lung cancer among people who 

 switch from unfiltered to filtered cigarettes is among 

 those who do not increase the number of cigarettes 

 they smoke per day.'* The risk in those who compen- 

 sate by smoking more than 10 additional filtered ciga- 

 rettes a day is as great as or greater than their risk 

 when they smoked unfiltered cigarettes. 



For myocardial infarction, studies comparing smok- 

 ers of high-yield and low-yield cigarettes, either old 

 style or modem, show no evidence of a difference in 

 disease risk.''^''"'" We can draw valid conclusions 

 concerning modem cigarettes and the risk of acute 

 myocardial infarction or sudden death, because these 

 events are closely related to current smoking habits. 

 The risk of these events diminishes within a year or 

 less of stopping smoking, so the brand most recendy 

 smoked is likely to influence disease risk. Although 

 conclusions about the relative risks of modem high- 

 yield and low-yield cigarettes cannot yet be reached 

 for cancer or chronic lung disease, studies using bio- 

 chemical markers of nicotine or smoke intake in peo- 

 ple who smoke various brands indicate only small dif- 

 ferences in exposure to the toxins of tobacco smoke. 

 Tlie expected reduction in disease risk for a person 

 who smokes a low-yield cigarette is small, although 

 the consequences of a small reduction in a population 

 of smokers could be considerable. 



On balance, the movement toward low-yield ciga- 

 rettes has been worthwhile, although in reducing the 

 risk of disease it may have reached the limit. There 

 are, however, potential risks in encouraging the smok- 

 ing of low-yield cigarettes. The availability of low- 

 yield cigarettes may make it easier for adolescents to 

 begin smoking. Additives, which enhance the flavor of 

 low-yield cigarettes, may be harmful, although no 

 data concerning this issue are available. Most impor- 

 tant, informadon about low-yield cigarettes may be 

 used to convince people that smoking is not as hazard- 

 ous as it once was. As a result, some smokers may 

 switch to low-yield cigarettes rather than quit. 



The implicadons of the low-yield cigarette differ for 

 physicians and public health planners. The benefits 

 for any person of smoking low-yield rather than high- 

 yield cigarettes are small, and the benefits of quitting 

 are great. Physicians should give their patients the 

 unequivocal message that low-yield cigarettes are not 

 safe cigarettes. The only reliable way to reduce the 

 adverse health consequences of smoking is to stop. 



