Is history of hypertension and apolipoprotein E (APOE) associated with intracerebral hemorrhage risk in participants stratified by self-reported race/ethnicity?
In this case-control study of 13 124 adults, having a copy of APOE ε4 alleles increased the risk for lobar intracerebral hemorrhage only in white individuals, but after propensity score matching for hypertension burden, Hispanic individuals showed the same risk of APOE ε4.
APOE ε4 appears to be confirmed as a risk factor for lobar intracerebral hemorrhage in nonwhite populations but is masked by differential hypertension burden in Hispanic individuals; further studies are needed to explore the interactions between APOE alleles and environmental exposures.
Genetic studies of intracerebral hemorrhage (ICH) have focused mainly on white participants, but genetic risk may vary or could be concealed by differing nongenetic coexposures in nonwhite populations. Transethnic analysis of risk may clarify the role of genetics in ICH risk across populations.
To evaluate associations between established differences in ICH risk by race/ethnicity and the variability in the risks of apolipoprotein E (APOE) ε4 alleles, the most potent genetic risk factor for ICH.
Design, Setting, and Participants
This case-control study of primary ICH meta-analyzed the association of APOE allele status on ICH risk, applying a 2-stage clustering approach based on race/ethnicity and stratified by a contributing study. A propensity score analysis was used to model the association of APOE with the burden of hypertension across race/ethnic groups. Primary ICH cases and controls were collected from 3 hospital- and population-based studies in the United States and 8 in European sites in the International Stroke Genetic Consortium. Participants were enrolled from January 1, 1999, to December 31, 2017. Participants with secondary causes of ICH were excluded from enrollment. Controls were regionally matched within each participating study.
Main Outcomes and Measures
Clinical variables were systematically obtained from structured interviews within each site. APOE genotype was centrally determined for all studies.
In total, 13 124 participants (7153 [54.5%] male with a median [interquartile range] age of 66 [56-76] years) were included. In white participants, APOE ε2 (odds ratio [OR], 1.49; 95% CI, 1.24-1.80; P < .001) and APOE ε4 (OR, 1.51; 95% CI, 1.23-1.85; P < .001) were associated with lobar ICH risk; however, within self-identified Hispanic and black participants, no associations were found. After propensity score matching for hypertension burden, APOE ε4 was associated with lobar ICH risk among Hispanic (OR, 1.14; 95% CI, 1.03-1.28; P = .01) but not in black (OR, 1.02; 95% CI, 0.98-1.07; P = .25) participants. APOE ε2 and ε4 did not show an association with nonlobar ICH risk in any race/ethnicity.
Conclusions and Relevance
APOE ε4 and ε2 alleles appear to affect lobar ICH risk variably by race/ethnicity, associations that are confirmed in white individuals but can be shown in Hispanic individuals only when the excess burden of hypertension is propensity score–matched; further studies are needed to explore the interactions between APOE alleles and environmental exposures that vary by race/ethnicity in representative populations at risk for ICH.
Marini S, Crawford K, Morotti A, et al. Association of Apolipoprotein E With Intracerebral Hemorrhage Risk by Race/Ethnicity: A Meta-analysis. JAMA Neurol. Published online February 06, 2019. doi:10.1001/jamaneurol.2018.4519
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