Correlation Between Timed Up and Go Test and Neuroimaging in Mexican American and Non-Hispanic Americans with Alzheimer’s Disease

Purpose:

Alzheimer's Disease (AD) is a progressive neurodegenerative disease that causes cognitive and functional impairments. Abnormal amyloid plaque accumulation is known to be specific for AD, demonstrated by previous amyloid Positron Emission Tomography (PET) studies showing abnormal amyloid plagues levels in subjects in the early stages of the disease, not exhibiting clinical manifestations. 1,2 Hispanic Americans are underrepresented in AD research. This study explores the possible relationship between the amyloid plaque level visible on amyloid PET scans and non-specific Physical Performance Tests such as Timed Up and Go (TUG) among Mexican Americans and non-Hispanic white American subjects. Furthermore, this study explores the possible correlation between rising amyloid plaque levels and declining function measured by simple physical performance tests such as TUG in outpatient clinics for AD patients.

Methods:

Data were analyzed on n= 2076 Participants (n= 1037 Non-Hispanic White, n=1039 Hispanic, Mexican American) from the Health and Aging Brain Study- Health Disparities All participants underwent as part of the HABS-HD protocol cognitive testing, functional/medical examination, blood draw, and neuroimaging. Amyloid PET scans (with Neuraceq/florbetaben F18) were conducted with defined regions of intertest (ROIs) included the frontal, anterior/posterior cingulate, lateral parietal, and lateral temporal cortex. All participants completed the Timed UP and Go (TUG) test along with other gait measures as part of the functional examine. The TUG is a measure of functional mobility, higher scores mean worse performance on the measure. Chi-square (Sex) and t-tests (Age, Education, TUG performance) were used to examine differences in demographic characteristics across ethnic groups. Linear regression models were conducted to examine the relationship between Amyloid PET imaging and a functional measure (TUG) and the significance was set at p<0.05

Results:

In our study, we found a statistically significant correlation between TUG time and increased amyloid uptake only in the lateral parietal region in Mexican American subjects (p=0.049). The other ROIs in Mexican American subjects showed no statistically significant correlation between TUG time and increased amyloid uptake. All ROIs in Non-Hispanic Whites showed no statistically significant correlation between TUG time and increased amyloid uptake.

Conclusion:

This study aimed to examine the relationship between physical performance measures (such as the TUG) and amyloid uptake. TUG is a non-specific physical performance measure often used in outpatient offices with older adult patients and is shown to correlate with cognitive decline.3 Using PET scans, we theorized that TUG results might correlate with the amyloid plaque level; however, our results were inconsistent with our initial hypothesis. On the other hand, this study did reveal a correlation between TUG time and increased amyloid uptake (only in the lateral parietal region) with subjects of Mexican descent, therefore; highlighting the importance of exploring ethnic differences in AD research. Finally, this study is limited by a small sample size, and future work with additional samples should help examine the TUG and amyloid uptake relationship and ethnic differences.