Apolipoprotein E ε4 Allele-Based Differences in Brain Volumes Are Largely Uniform Across Late Middle Aged and Older Hispanic/Latino- and Non-Hispanic/Latino Whites Without Dementia

Abstract

Hispanics/Latinos are at an equal or a greater risk for Alzheimer's disease (AD), yet risk factors remain more poorly characterized as compared to non-Hispanic/Latino Whites. Among non-Hispanic/Latino White cohorts, the apolipoprotein E (APOE) ε4 allele is one of the strongest risk factors for AD with subtle declines in episodic memory and brain volumes detectable in the preclinical stages. We examined whether the APOE ε4 status had a differential impact on cognition and brain volumes among cognitively healthy and mild cognitively impaired Hispanics/Latinos (n = 86; ε4 n = 23) compared to a well-matched group of non-Hispanic/Latino Whites (n = 92; ε4 n = 29). Neither the APOE ε4 status nor the interaction between the ε4 status and ethnicity was associated with cognitive performance. The APOE ε4 status was associated with white matter and not with gray matter volumes. APOE ε4 carriers had a significantly smaller total brain white matter volumes, as well as smaller right middle temporal and left superior temporal volumes. The Hispanics/Latinos had significantly smaller left middle frontal gray matter volumes, yet marginally larger overall white matter volumes, than the non-Hispanic/Latino Whites. Exploratory analysis within the Hispanic/Latino sample found that those people whose primary language was Spanish had larger total brain white matter volumes compared primarily to the English speakers. Importantly, primary language differences only held for Hispanic/Latino ε4 carriers and did not differentiate Hispanic/Latino non-carriers, underscoring the need for further investigation into the impacts of language and acculturation on cognitive aging among the fastest growing ethnic minority group in the United States.

Characterizing age- and sex-related differences in brain structure among middle-aged and older Hispanic/Latino adults in the study of Latinos- investigation of neurocognitive aging magnetic resonance imaging (SOL-INCA MRI)

“…For example, white matter hyperintensities (WMHs), a measure of cerebrovascular disease, is greater among U.S. Caribbean Hispanic/Latino adults ( Brickman et al, 2008 ; Zahodne et al, 2015 ) but similar or reduced in predominantly Mexican American samples ( DeCarli et al, 2008 ; Mungas et al, 2009 ) when compared to non-Hispanic/Latino White individuals. More consistently, middle-aged and older Hispanic/Latino individuals have larger global brain volumes and/or smaller ventricle size compared to their non-Hispanic/Latino White counterparts which may indicate differences in underlying brain aging patterns ( Brickman et al, 2008 ; Burke et al, 2018 ; DeCarli et al, 2008 ; Minagar et al, 2000 ; Stickel et al, 2021 ). Despite these distinctions, other factors, such as sex differences which tend to favor larger global brain volumes and region-specific morphometrics in women when adjusting for head size ( Cowell et al, 1994 ; Driscoll et al, 2009 ; Geerlings et al, 2010 ; Raz et al, 2004a ) remain relatively unexplored in the Hispanic/Latino aging brain ( McKay et al, 2014 ; Prabhakaran et al, 2008 ).…”