Interactive effects of age and other risk factors on long-term survival after coronary artery surgery

The effect of age at the time of coronary artery bypass graft surgery on postoperative survival was studied in 2,507 patients with significant coronary artery disease. Patients were subdivided into five groups based on age at the time of surgery: 20 to 39, 40 to 49, 50 to 59, 60 to 69 and greater than or equal to 70 years. The observed death rate was compared with that expected for subjects from the general U.S. population matched for age, gender, race and calendar year. For patients less than or equal to 59 years of age, the ratio of observed to expected death rates was significantly greater than unity (observed/expected = 4.9 for ages 20 to 39, 1.9 for ages 40 to 49 and 1.3 for ages 50 to 59 years, p less than 0.01). The prevalence of risk factors, including diabetes mellitus, hypertension, hypercholesterolemia and cigarette smoking, was evaluated in the different age subgroups. When patients were subdivided on the basis of history of cigarette smoking, the decreased relative survival rate of younger (less than 60 years old) patients existed only in those who smoked (observed/expected = 6.0 for ages 20 to 39, 2.2 for ages 40 to 49 and 1.4 for ages 50 to 59 years). In nonsmokers, observed/expected ratios for every age group were not significantly different from unity. Thus, the reduced relative survival rate of younger patients after coronary artery bypass graft surgery may be attributed to the interactive harmful effects of cigarette smoking.