meta-analysis of aspirin and subarachnoid hemorrhage in patients with intracranial aneurysms yields different results to the general population.

BACKGROUND: Some studies have shown a protective association between aspirin use and subarachnoid hemorrhage. Other studies have found no relationship or the reverse. These studies differ in their study populations and definitions of subarachnoid hemorrhage. AIMS: Our aim was to establish (1) if there is an association between aspirin and subarachnoid hemorrhage, (2) how this differs between the general population and those with intracranial aneurysms. SUMMARY OF REVIEW: Studies reporting aspirin use and the occurrence of subarachnoid hemorrhage were included and grouped based on population (general population vs. aneurysm population). Odds ratios, hazard ratios, and confidence intervals were combined in random-effects models. Eleven studies were included. Overall, there was an association between aspirin and subarachnoid hemorrhage (OR 0.68 [0.48, 0.96]). However, populations were diverse and heterogeneity between studies high (p < 0.00001), questioning the validity of combining these studies and justifying analysis by population. In the general population, there was no difference in aspirin use between individuals with and without subarachnoid hemorrhage (OR 1.15 [0.96, 1.38]). In patients with intracranial aneurysms, aspirin use was greater in patients without subarachnoid hemorrhage (OR 0.37 [0.24, 0.58]), although these studies were at higher risk of bias. CONCLUSIONS: There is an association between aspirin use and subarachnoid hemorrhage in patients with intracranial aneurysms. This apparent protective relationship is not seen in the general population. Prospective randomized studies are required to further investigate the effect of aspirin on unruptured intracranial aneurysms.