Intraindividual variability of cognitive performance and associations with magnetic resonance imaging in aging American Indians: Data from the Strong Heart Study

Abstract

AbstractBackgroundAmerican Indians present with increased risk factors for Alzheimer’s disease and related dementias (ADRDs). Intraindividual cognitive variability (IICV), which measures the variability in performance on neuropsychological tests within a person at a single time, has been proposed as a noninvasive marker of neurodegeneration and early dementia. In this study, we investigated the hypothesis that higher IICV was related to more features of neurodegeneration on magnetic resonance imaging (MRI) measurements among older American Indians.MethodAmerican Indian participants over 64 years of age who underwent MRI and completed a battery of neuropsychological tests were included in the study (N = 750). Data from three neuropsychological tests were used to compute a multidomain IICV measure of cognition along with IICV measures representing the cognitive domains of memory, executive function and processing speed. Regression models estimated IICV associations with total brain volume, hippocampal volume, and graded white matter disease, adjusting for age, sex, education, BMI, and intracranial volume.ResultMemory, executive function and processing speed, and multidomain IICV measures were associated with total brain volume before correction for multiple comparisons. After correction with Bonferroni, only higher IICV of memory was associated with lower total brain volume (Beta = −0.20; 95%CI −0.332, −0.068; p = 0.009). Furthermore, additional adjustment of mean scores from the tests used for the variability measure resulted in loss of significance for all IICV measures, with only mean scores remaining significant. Measures of IICV were not associated with hippocampal volume or white matter disease.ConclusionThese findings suggest that IICV of memory may be associated with imaging measures related to neurodegenerative injury in older American Indians. However, these associations representing variability in cognition are smaller than those representing mean cognition. More research is needed to understand the clinical and etiologic associations for IICV measures.