BACKGROUND

Given the premise that certain bacteria (such as Chlamydia pneumoniae) may play a role in the etiology of atherosclerosis, subjects treated with antibiotics that have antibacterial activity against C pneumoniae may be at lower risk for the development of an acute myocardial infarction (MI) than untreated subjects.

METHODS

A case-control design, nested within a cohort of 29,937 elderly subjects in whom antihypertensive therapy was initiated (1982-1995) was used, in which each subject who was hospitalized with a primary discharge diagnosis of MI between 1987 and 1995 (n = 1047) was matched on calendar time to 5 randomly selected control subjects for exposure contrasts. Conditional logistic regression analyses were conducted to adjust for predisposing factors for MI.

RESULTS

Although no clear consistent effect of antibiotics use was found in relation to MI, a trend was observed for a decreased risk of acute MI in patients receiving a prescription for antichlamydial antibiotics in the preceding 3 months (odds ratio 0.68, 95% CI 0.46-1.00). Antibiotics without antichlamydial activity showed no benefit in MI risk.

CONCLUSIONS

The beneficial effect of certain antichlamydial antibiotics in reducing the risk of MI cannot be excluded on the basis of this representative cohort of elderly patients in a routine clinical care setting. Larger prospective studies are required to confirm the usefulness of antibiotics in the primary prevention of MI.