ORAL-CONTRACEPTIVES AND THE RISK OF SUBARACHNOID HEMORRHAGE - A METAANALYSIS

Objective: The objective of this study is to estimate the risk of suba rachnoid hemorrhage produced by oral contraceptive use. Methods: Studi es published since 1960 were identified using MEDLINE, Cumulated Index Medicus, Dissertation Abstracts On-line, and bibliographies of pertin ent articles. Two independent reviewers screened published cohort and case-control studies that evaluated the risk of subarachnoid hemorrhag e associated with oral contraceptives. Eleven of 21 pertinent studies met predefined quality criteria for inclusion in the meta-analysis. Re lative risk (RR) estimations evaluating subarachnoid hemorrhage risk i n oral contraceptive users compared with nonusers were extracted from each study by two independent reviewers. Study heterogeneity was asses sed by design type, outcome measure (mortality versus incidence), expo sure measure (current versus ever use), prevailing estrogen dose used, and control for smoking and hypertension. Results: The overall summar y RR of subarachnoid hemorrhage due to oral contraceptive use was 1.42 (95% CI, 1.12 to 1.80; p = 0.004). When the two study results failing to control for smoking were excluded from the analysis, a slightly gr eater effect was seen, with an RR of 1.55 (95% CI, 1.26 to 1.91; p < 0 .0001). In the six studies controlling for smoking and hypertension th e RR was 1.49 (95% CI, 1.20 to 1.85; p = 0.0003). High-estrogen oral c ontraceptives appeared to impart a greater risk than low-dose preparat ions in studies controlling for smoking, but the difference was not si gnificant (high-dose RR, 1.94; 95% CI, 1.06 to 3.56; low-dose RR, 1.51 ; 95% CI, 1.18 to 1.92). Conclusions: This meta-analysis of observatio nal studies suggests that oral contraceptive use produces a small incr ease in the risk of subarachnoid hemorrhage.