Risk of ischemic stroke associated with low-dose oral contraceptive use: a meta-analysis

Abstract

Context: Oral contraceptive (OC) use has been shown to be associated with increased risk of ischemic stroke. However, most studies were conducted before low-dose OC became available.Objective: To determine whether low-dose OC use is associated with increased risk of ischemic stroke Data Sources: All relevant human-subject and English-language studies in MEDLINE, EMBASE, and Science Citation Index from January 1970 through February 2005Study Selection and Data Extraction: All published studies of OC or estrogen with any type of stroke as an outcome were included. Studies were excluded if they included populations at high risk for ischemic stroke or did not include low-dose OC use, ischemic stroke, or a control group. Data Synthesis:A meta-analysis of the nine included studies showed positive association between current low-dose OC use and ischemic stroke (Overall pooled odds ratio [OR], 2.1; 95% confidence interval [CI], 1.7 -2.7). Compared to never users, current users had slightly higher risk (OR, 1.2; 95% CI, 0.4 -3.2) and former users had significantly lower risk (OR, 0.6; 95% CI, 0.5 -0.7). Current users of second and third generation OC had 2.4 times (95% CI, 2.0 -3.0) and 2.0 times (95% CI, 1.3 -3.0) increased risk of ischemic stroke, respectively, compared to former or never users. The independent effect of low-dose OC use on the risk of ischemic stroke was stronger among women less than 35 years, nonsmokers, and normotensive women.Conclusion: Current use of low-dose OC compared to former or never use is associated with about two times increased risk of ischemic stroke. However, considering its health benefits and effectiveness of birth control and very low incidence of ischemic stroke in young women, use of low-dose OC is generally safe.