Abstract

PIP: Researchers conducted a population-based, retrospective, case control study to determine whether or not women using combined oral contraceptives (OCs) containing less than 50 mcg estrogen face an increased risk for hemorrhagic or ischemic stroke. The racially and ethnically diverse group of 1.1 million women 15-44 years old was enrolled in the Kaiser Permanente Medical Plans of northern and southern California. The women were observed for over 3.6 million women-years. 408 of the women had suffered a stroke during 1991-1994, for an incidence rate of 11.3/100,000 women-years. Compared to former users and never users, among current OC users the adjusted odds ratio was 1.18 for ischemic infarction (95% confidence interval [CI], 0.54-2.59) and 1.14 for hemorrhagic stroke (95% CI, 0.60-2.16). That the CI for the odds ratios include 1.00 suggests that current OC users do not face a significantly increased risk for stroke overall. Current OC use combined with smoking did appear to affect the outcome of hemorrhagic stroke. Limitations of the study include: the women had consistent access to medical care at little or no cost (different results may have been seen among poor women at public clinics), the low risk of stroke in young women limits the statistical power of the study, and the researchers did not inquire about migraine in study participants. These findings imply that most users of and potential candidates for low-dose OCs face little or no increased risk for stroke. Among non-smokers regardless of age, the risk of death from pregnancy is greater than it is from OC use. Among smokers 40 years or younger, the risk of death as a result of pregnancy may be higher than that due to OC use, still smokers 35 and older should not use OCs.