Relationships between Cardiovascular Risk Factors, Brain Structure, and Cognition in Older Hispanics Compared to Non-Hispanic Whites

Abstract

Relative to non-Hispanic Whites, Hispanics have longer lifespan (Lariscy, Hummer, & Hayward, 2015), yet little is known about cognition and daily functioning among this growing older adult group. Among non-Hispanic Whites, both cardiovascular risk factors (e.g., hypertension and obesity) and genetic risk factors for Alzheimer’s disease (e.g., the apolipoprotein (APOE) ε4 allele) impact cognition in late middle age and older adulthood. History of hypertension, obesity, and the APOE ε4 allele are associated with lower scores on episodic memory and executive functioning measures though findings are mixed. Neuroimaging data supports the notion that each of the mentioned risk factors likely impacts brain structure (e.g., brain volumes, white matter integrity) which then, in turn, impacts cognition. Hispanics (n = 91) and non-Hispanic Whites (n = 92), ages 50 – 94, were carefully selected from the National Alzheimer’s Coordinating Center (NACC) and Alzheimer’s Disease Neuroimaging Initiative (ADNI) in order to have groups matched on age, education, and gender. Using this sample across all studies, we tested how ethnicity (Hispanic versus non-Hispanic White) influenced the following: 1) the associations between daily functioning and cognition (episodic memory, executive functioning, and processing speed), 2) the separate impacts of hypertension and obesity on episodic memory and executive functioning, 3) the separate associations between hypertension and obesity on gray and white matter volumes and the ability for cardiovascular risk-associated volumes to predict episodic memory, executive functioning, and processing speed, and 4) the relationships between APOE ε4 status on gray and white matter volumes and cognition (i.e., episodic memory, executive functioning, and processing speed). We found that lower memory scores were uniformly associated with worse daily functioning across ethnic groups whereas slower processing speed was only associated with worse daily functioning for non-Hispanic Whites. Hypertension and high body mass index (a measure of obesity) were associated with lower executive functioning performances among Hispanics to a greater degree than among non-Hispanic Whites. Across both ethnic groups, BMI was not associated with brain volumes while hypertension was unexpectedly associated with larger gray matter volumes in mid-to-posterior brain regions, ranging from postcentral gyrus to middle occipital gyrus. Notably, larger gray matter volumes in the right parietal cortex were associated with slower task switching among Hispanics but faster performance among non-Hispanic Whites. Memory, working memory, and processing speed were best predicted by demographics (age and/or ethnicity). Finally, APOE ε4 carriers had lower white matter volumes in bilateral temporal regions relative to non-carriers. Within the left middle frontal gyrus, Hispanics had smaller gray matter volumes compared to non-Hispanic Whites. APOE ε4 status was not predictive of cognition. At the level of the brain, the impacts of hypertension and APOE ε4 status on brain volumes tended to be consistent across ethnic groups whereas effects on cognition and daily functioning suggests more mixed, uniform and ethnicity-specific findings.