Tar yield of cigarettes and risk of acute myocardial infarction. GISSI-EFRIM Investigators.

OBJECTIVE--To analyse the relation between tar and nicotine yield of cigarettes smoked in the recent past and the risk of myocardial infarction. DESIGN--Multicentre case-control study conducted between September 1988 and June 1989. SETTING--Over 80 coronary care units in various Italian regions. SUBJECTS--916 patients with acute myocardial infarction without history of ischaemic heart disease and 1106 controls admitted to hospital for acute conditions not related to known or suspected risk factors for ischaemic heart disease. MAIN OUTCOME MEASURES--Relative risk of myocardial infarction according to type of cigarette smoked adjusted for identified potential confounding factors. Brands of cigarettes classified according to yield of tar and nicotine. RESULTS--Patients with acute myocardial infarction were more often smokers and among smokers they tended to smoke more cigarettes. Compared with non-smokers their estimated relative risks were 3.8, 4.3, 3.2, and 3.7 in the four categories of tar yield (< 10, 10-15, > 15-20, and > 20 mg, respectively). No trend in risk across yields was evident when analysis was restricted to smokers and allowance was made for number of cigarettes. Compared with risks in subjects in the lowest category of tar yield the relative risks were 1.2, 0.8, and 1.0 for the subsequent yields. Compared with risks in non-smokers the relative risks ranged from 9.3 to 12.6 below the age of 50 but no trend was observed with increasing yield. CONCLUSIONS--Changing to cigarettes with a lower tar yield is not an effective means of reducing tobacco related morbidity from myocardial infarction.