Background and Purpose--An increasing number of reports have linked infections to atherosclerosis and thrombosis. Thus, use of antibiotics may lower the risk of developing cerebrovascular disease. We investigated whether antibiotic use is associated with the risk of stroke in elderly individuals treated for hypertension.

Methods--A cohort of 29 937 elderly subjects initiating antihypertensive therapy between 1982 and 1995 was formed from the Quebec healthcare insurance database. A nested case-control design was used in which each subject hospitalized with a primary discharge diagnosis of stroke between 1987 and 1995 was matched on calendar time to 5 randomly selected controls from the cohort. Conditional logistic regression was used to estimate odds ratios of stroke after adjustment for predisposing factors.

Results--We identified 1888 cases and 9440 controls. The overall adjusted odds ratio for current antibiotic use was 0.80 (95% confidence interval, 0.63 to 1.01), and that for recent use was 0.81 (95% confidence interval, 0.70 to 0.94). Penicillin was the only individual antibiotic class that showed a protective association across different time windows. No significant association was found between stroke risk and the use of fluoroquinolones, macrolides, tetracyclines, or cephalosporins.

Conclusions--Although no clear, consistent associations between overall antibiotic use and cerebrovascular disease could be found, an intriguing association between penicillin use and stroke should be explored further.