ACUTE MYOCARDIAL-INFARCTION - ASSOCIATION WITH TIME SINCE STOPPING SMOKING IN ITALY

Study objective - The study aimed to investigate the relationship betw een years since stopping smoking and the risk of acute myocardial infa rction. Design - This was a hospital based, multicentre, case-control study conducted in Italy between September 1988 and June 1989 within t he framework of the GISSI-2 clinical trial. Setting - Over 80 coronary care units in various Italian regions participated.Subjects - A total of 916 incident cases of acute myocardial infarction, below age 75 ye ars, and with no history of ischaemic heart disease, and 1106 control subjects admitted to the same hospitals for acute, non-neoplastic, car diovascular or cerebrovascular conditions that were not known or suspe cted to be related to cigarette smoking took part in the study. Main o utcome measures and results - Measures were relative risk (RR) estimat es of acute myocardial infarction according to the time since stopping smoking and adjusted for identified potential confounding factors. Co mpared with never smokers, the multivarlate RRs were 1.6 (95% confiden ce interval (CI) 0.8,3.2) for subjects who had given up smoking for on e year; 1.4 (95% CI0.9,2.1) for those who had stopped for two to five years; 1.2 (95% CI0.7,2.1) for six to 10 years; and 1.1 (95% CI0.8,1.8 ) for those who had not smoked for over 10 years. The estimated RR for current smokers was 2.9 (95% CI 2.2,3.9). The risks of quitters were higher for heavier smokers and those below age 50 years, while no diff erence emerged in relation to the duration of smoking, sex, and other risk factors for myocardial infarction. Conclusions - These results in dicate that there is already a substantial drop in the risk of acute m yocardial infarction one year after stopping. The risk in ex-smokers, however, seemed higher (although not significantly) than that of those who had never smoked, even more than 10 years after quitting. This co uld support the existence of at least two mechanisms linking cigarette smoking with acute myocardial infarction - one involving thrombogenes is or spasms that occurs over the short term, and another involving at herosclerosis that is a long term effect.