Aspirin Use and Risk of Subdural Hematoma: Updated Meta-Analysis of Randomized Trials.

BACKGROUND AND PURPOSE: Subdural hematomas are an uncommon, but a serious, bleeding complication of antithrombotic therapies. We update our previous inconclusive meta-analysis to better estimate the risk of subdural hematoma associated with aspirin use. METHODS: For the initial meta-analysis, nine randomized trials published between1980 and 2012 comparing aspirin with placebo/control were considered. Additional data from four large primary prevention trials were added. Two reviewers independently extracted data on subdural hematomas, with differences resolved by joint review and consensus. RESULTS: Numbers of subdural hematoma were available from thirteen randomized trials involving 155,554 participants comparing aspirin (dosage range 25 mg twice daily to 325 mg daily) to placebo (ten double-blind trials) or no aspirin (three trials). Participants included healthy healthcare providers, older people with vascular risk factors without manifest vascular disease, and those with atrial fibrillation or chronic angina. Pooling all trials, subdural hematomas were identified in 93 of 77,698 participants assigned to aspirin versus 62 of 77,856 participants assigned to placebo/no aspirin. By meta-analysis, the relative risk ratiometa of subdural hematoma associated with assignment to aspirin was 1.5 (95%CI 1.1, 2.0, p = 0.01; p = 0.9 for heterogeneity, I2 index = 0%). Based on recent primary prevention trials, subdural hematoma diagnosis averaged 1 per 3,125 people per year without aspirin use; the absolute increase associated with aspirin use was estimated as one additional subdural hematoma per 6,500 patients annually. CONCLUSIONS: This meta-analysis confirms that aspirin use increases the relative risk of subdural hematoma, but the absolute increased rate associated with aspirin therapy is very low for most people.

Vitamin K antagonists and risk of subdural hematoma: meta-analysis of randomized clinical trials.

BACKGROUND AND PURPOSE: Subdural hematomas are an important bleeding complication of anticoagulation. We quantify the risk of subdural hematoma associated with anticoagulation with vitamin K antagonists (VKAs) compared with other oral antithrombotic therapies. METHODS: Randomized trials were identified from the Cochrane Central Register of Controlled Trials and were included if published since 1980 and compared oral VKAs with antiplatelet therapy or with direct-acting oral anticoagulants. Two reviewers independently extracted data with differences resolved by joint review. RESULTS: Nineteen randomized trials were included that involved 92 156 patients and 275 subdural hematomas. By meta-analysis, VKAs were associated with a significantly increased risk of subdural hematoma (odds ratios, 3.0; 95% confidence interval, 1.5-6.1) compared with antiplatelet therapy (9 trials, 11 603 participants). The risk of subdural hematoma was also significantly higher with VKAs versus factor Xa inhibitors (meta-analysis odds ratios, 2.9; 95% confidence interval, 2.1-4.1; 5 trials, 49 687 patients) and direct thrombin inhibitors (meta-analysis odds ratios, 1.8; 95% confidence interval, 1.2-2.7; 5 trials, 30 866 patients) versus VKAs. The absolute rate of subdural hematoma among 24 485 patients with atrial fibrillation treated with VKAs pooled from 6 trials testing direct-acting oral anticoagulants was 2.9 (95% confidence interval, 2.5-3.5) per 1000 patient-years. CONCLUSIONS: VKA use significantly increases the risk of subdural hematoma by ≈3-fold relative to antiplatelet therapy. Direct-acting oral anticoagulants are associated with a significantly reduced risk of subdural hematomas versus VKAs. Based on indirect comparisons to VKAs, the risks of subdural hematoma are similar with antiplatelet monotherapies and factor Xa inhibitors.

Aspirin therapy and risk of subdural hematoma: meta-analysis of randomized clinical trials.

BACKGROUND: Subdural hematomas are an important bleeding complication of antithrombotic therapies. We sought to characterize the risk of subdural hematoma associated with antiplatelet therapy. METHODS: Trials were gathered from the Cochrane Central Register of Controlled Trials and from recent meta-analyses of trials regarding antiplatelet therapy for the primary prevention of stroke. Randomized trials published since 1980 comparing antiplatelet therapy with placebo or control and reporting subdural hematoma were included in the analysis. For recent large trials that did not report subdural hematomas, unpublished results were sought. Two reviewers independently extracted data on study design and subdural hematomas, with differences resolved by joint review and consensus. RESULTS: Four published trials were identified that compared aspirin with placebo/control involving 6565 participants (mean age 66 years) with 8 total subdural hematomas. Unpublished data from 5 aspirin trials with 90,689 participants reported 18 total subdural hematomas. The incidence of subdural hematomas varied from 0.02 per 1000 patient-years for primary prevention trials of middle-aged health professionals to 1 to 2 per 1000 patient-years for older patients with atrial fibrillation. Pooled data from all 9 trials revealed an odds ratio of 1.6 (95% confidence interval 0.8-3.5; heterogeneity P = .8; I(2) index 0%) for antiplatelet therapy and risk of subdural hematoma. CONCLUSIONS: Based on the limited available data, it is uncertain whether aspirin therapy increases the risk of subdural hematoma: the observed 1.6-fold increased risk was not statistically significant. The incidence of subdural hematoma during aspirin therapy is low but varies widely depending upon the age of the patient population.