1. In this systematic review and meta-analysis, use of low-dose aspirin in patients without symptomatic cardiovascular disease was linked with an increased risk of intracranial hemorrhage (ICH).
2. Risk of ICH was greatest amongst those with low body mass, or Asian ethnicity.
Evidence Rating Level: 1 (Excellent)
Study Rundown: The use of low-dose aspirin for symptomatic atherosclerotic disease has well-established efficacy. Data suggest this benefit does not translate to primary prevention, and data suggest potential harm. Intracranial hemorrhage is of particular concern given the substantial associated morbidity and mortality. The current study is a systematic review and meta-analysis of available randomized clinical trials evaluating the risk of ICH in patients without symptomatic cardiovascular disease receiving low-dose aspirin or placebo/no aspirin. The study found an overall increase risk of ICH in the aspirin group, with a greater risk of subdural or extradural hemorrhage. The risk of ICH was also greater in patients who were low body mass index or of Asian ethnicity.
The main strength of the study include the large number of patients included in the meta-analysis allowing for accurate estimation of the absolute risk of ICH. The main limitation of the study is the paucity of trials with ethnic diversity, with only one trial from Japan including predominantly Asian participants.
In-Depth [systematic review and meta-analysis]: This study was a systematic review and meta-analysis of randomized clinical trials that included a comparison between arms taking aspirin and no aspirin or placebo. Trials were included if they had aspirin doses 100 mg/day or less, reported ICH as an endpoint with results reported for each group of patients, and had treatment duration of at least 6 months. Trials were excluded if participants had pre-existing symptomatic cardiovascular disease, or used additional antithrombotic agents in either the study or control arms.
The study included 134,446 patients from 13 clinical trials of low-dose aspirin for primary prevention. The risk of ICH was greater in the aspirin group (relative risk, 1.37; 95%CI, 1.13-1.66; 2 additional intracranial hemorrhages in 1000 people) compared to the control group. The observed increase in ICH was greater for Asian populations (RR 1.84, 95% CI, 1.04-3.27) and patients with a BMI less than 25 (RR 1.84, 95% CI, 1.04-3.27).
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