Apolipoprotein E (APOE) ε4 and ε2 alleles appear to affect lobar intracerebral hemorrhage (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. This according to a recent study that aimed to evaluate associations between established differences in ICH risk by race/ethnicity and the variability in the risks of APOE ε4 alleles, the most potent genetic risk factor for ICH. Researchers conducted a case-control study of primary ICH that 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. They found:

• 13,124 participants (7,153 [54.5%] male with a median [interquartile range] age of 66 [56-76] years) were included.

• In white participants, APOE ε2 and APOE ε4 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 but not in black participants.