Huo, Shufan

Importance The APOE ε4 variant is causally linked to cerebral amyloid angiopathy and is a risk factor for intracranial hemorrhage (ICH) among warfarin-treated patients with atrial fibrillation. Nevertheless, its impact on those treated with apixaban remains unknown. Objective To test the hypothesis that APOE ε4 allele carriership is associated with an increased risk of ICH in patients with atrial fibrillation taking apixaban. Design, Setting, and Participants This cohort study involved data from the All of Us Research Program, a longitudinal, population-based study in the United States. Inclusion criteria were age older than 50 years, history of atrial fibrillation, and anticoagulation with apixaban. Participants with a history of ischemic stroke or ICH were excluded. Up to 3 years of follow-up data were available. Data were collected from 2017 to 2022 and analyzed from November 2023 to December 2024. Exposure APOE ε2, ε3, and ε4 were ascertained using variants rs429358 and rs7412. APOE ε4 was modeled dichotomously (noncarriers [no alleles] vs carriers [1 or 2 alleles]). Main Outcomes and Measures Incident ICH, including any new intraparenchymal, subdural, or subarachnoid hemorrhage after initiation of apixaban therapy. Results Of 413 477 All of Us participants, 2038 were eligible. Their mean (SD) age was 71 (9) years; 918 (45%) were female, 1120 (55%) were male, and 1710 (83%) had European ancestry. Among these participants, 483 (23.7%) were carriers of at least 1 APOE ε4 allele. After a median follow-up of 2.9 years, 26 participants sustained an ICH (cumulative incidence, 1.5%; 95% CI, 1.0%-2.2%), of whom 12 (cumulative incidence, 3.1%; 95% CI, 1.7%-5.3%) were carriers and 14 (cumulative incidence, 1%; 95% CI, 0.6%-1.7%) were noncarriers ( P = .007). Multivariable Cox proportional hazard models confirmed this association: compared with noncarriership, APOE ε4 carriership was associated with a 3-fold increase in the risk of ICH (hazard ratio, 3.07; 95% CI, 1.42-6.65). APOE information improved the discrimination of risk prediction scores (C statistic of 0.74 and 0.68 for models with and without APOE , respectively; P = .03). Conclusions and Relevance Further research is needed to evaluate whether cerebral amyloid angiopathy mediates the observed association and whether APOE e4 information improves clinical decision-making about anticoagulation therapy in patients with atrial fibrillation. The latter is important now that APOE information is used in clinical settings to guide antiamyloid treatment for Alzheimer disease and has been returned to millions of persons by direct-to-consumer genotyping companies.

Introduction: Coagulation factor XI (FXI) inhibitors have shown a better safety profile than other anticoagulants, offering similar reductions in ischemic stroke (IS) risk with a lower risk of intracerebral hemorrhage (ICH). The APOE ε4 genotype is associated with increased risks of both IS and ICH, likely due to its effects on lipid levels, intracranial atherosclerosis, and cerebral amyloid angiopathy. We hypothesized that APOE ε4 carriers would gain greater therapeutic benefit from genetically reduced FXI levels compared to non-carriers. Methods: We conducted a two-stage Mendelian randomization (MR) analysis using the random-effects, inverse-variance weighted method. First, we estimated the effect of genetically proxied FXI inhibition on IS and ICH risk in the general population using summary data from genome-wide association studies of FXI levels (16,169 participants), IS (1,503,898 controls and 110,182 cases), and ICH (3,745 controls and 3,226 cases). Second, we performed stratified analyses to estimate the effect of genetically determined FXI levels on IS (10,343 cases and 476,838 controls) and ICH (2,236 cases and 484,945 controls) risk across APOE ε4 carriership strata (0, 1, or 2 alleles) using UK Biobank data. Results: In the general population, random-effects, inverse-variance weighted MR analyses showed that every 1 unit decrease in natural log-transformed FXI levels was associated with a 37% reduction in IS risk (OR:0.63; 95%CI:0.52–0.77; p <0.001) without a significant increase in ICH risk (OR:0.86; 95%CI:0.37–2.00; p =0.73). Stratified MR analyses indicated that genetically determined reductions in FXI levels had varying protective effects on IS risk based on APOE ε4 status: 31% in non-carriers (OR:0.69, 95%CI:0.53–0.91; p =0.008), 43% in carriers of 1 allele (OR:0.57, 95%CI:0.36–0.91; p =0.02), and 75% in carriers of 2 alleles (OR:0.25, 95%CI:0.06–1.06; p =0.06). Similar MR analyses showed no significant increase in ICH risk with genetically determined reductions in FXI levels in any APOE ε4 strata (all p >0.38, Figure 1). Conclusion: This two-stage genetic study provides causal evidence that lower FXI levels reduce IS risk in the general population, with an even stronger effect among APOE ε4 carriers, while not increasing ICH risk. These results indicate that FXI inhibitors might be a safer and more effective alternative to other anticoagulants among APOE ε4 carriers, who are known to be at higher risk for both ischemic and hemorrhagic events.