CIGARETTE-SMOKING, TAR YIELDS, AND NONFATAL MYOCARDIAL-INFARCTION - 14000 CASES AND 32000 CONTROLS IN THE UNITED-KINGDOM

Objectives-To assess the effects of cigarette smoking on the incidence of non-fatal myocardial infarction, and to compare tar in different t ypes of manufactured cigarettes. Methods-In the early 1990s responses to a postal questionnaire were obtained from 13 926 survivors of myoca rdial infarction (cases) recently discharged from hospitals in the Uni ted Kingdom and 32 389 of their relatives (controls). Blood had been o btained from cases soon after admission for the index myocardial infar ction and was also sought from the controls. 4923 cases and 6880 contr ols were current smokers of manufactured cigarettes with known tar yie lds. Almost all tar yields were 7-9 or 12-15 mg/cigarette (mean 7.5 mg for low tar (<10 mg) and 13.3 for medium tar (greater than or equal t o 10 mg)). The cited risk ratios were standardised for age and sex and compared myocardial infarction rates in current cigarette smokers wit h those in non-smokers who had not smoked cigarettes regularly in the past 10 years. Results-At ages 30-49 the rates of myocardial infarctio n in smokers were about five times those in non-smokers (as defined); at ages 50-59 they were three times those in non-smokers, and even at ages 60-79 they were twice as great as in non-smokers (risk ratio 6.3, 4.7, 3.1, 2.5, and 1.9 at 30-39, 40-49, 50-59, 60-69, 70-79 respectiv ely; each 2P<0.00001). After standardisation for age, sex, and amount smoked, the rate of non-fatal myocardial infarction was 10.4% (SD 5.4) higher in medium tar than in low tar cigarette smokers (2P=0.06). Thi s percentage was not significantly greater at ages 30-59 (16.6% (7.1)) than at 60-79 (1.0% (8.5)). In both age ranges the difference in risk between cigarette smokers and non-smokers was much larger than the di fference between one type of cigarette and another (risk ratio 3.39 an d 3.95 at ages 30-59 for smokers of similar numbers of low and of medi um tar cigarettes, and risk ratio 2.35 and 2.37 at ages 60-79). Most p ossible confounding factors that could be tested for were similar in l ow and medium tar users, with no significant differences in blood lipi d or albumin concentrations. Conclusion-The present study indicates th at the imminent change of tar yields in the European Union to comply w ith an upper limit of 12 mg/cigarette will not increase (and may somew hat decrease) the incidence of myocardial infarction, unless they indi rectly help perpetuate tobacco use. Even low tar cigarettes still grea tly increase rates of myocardial infarction, however, especially among people in their 30s, 40s, and 50s, and far more risk is avoided by no t smoking than by changing from one type of cigarette to another.