Amyloid and tau PET in relation to longitudinal change in subjective cognitive complaints among cognitively normal individuals
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Background and Objectives
Subjective cognitive complaints often precede declines in objective measures of cognitive performance and may facilitate the early diagnosis of cognitive impairment. This study examined whether amyloid and tau pathology are associated with level and longitudinal change in subjective cognitive complaints among cognitively normal individuals, and compared these associations to those observed with objective neuropsychological measures of verbal episodic memory performance.
Methods
Amyloid and tau pathology were measured by 11 C-Pittsburgh compound B (PiB) and 18 F-flortaucipir (FTP) PET scans, respectively. FTP PET regions of interest (ROIs) included the entorhinal cortex, hippocampus, parahippocampal gyrus, and inferior temporal gyrus. Subjective cognitive complaints were assessed using the Cognitive Failures Questionnaire (CFQ). California Verbal Learning Test (CVLT) immediate and long-delayed free recall scores were used to quantify objective memory performance. We examined the association of PET measures with rates of change in CFQ and verbal memory within 5 years of the PET scans using linear mixed effects models.
Results
We analyzed data for 92 cognitively normal participants in the Baltimore Longitudinal Study of Aging (BLSA). In analyses that included both amyloid positivity and regional tau burden as predictors greater parahippocampal tau standardized uptake value ratio (SUVR) was associated with higher CFQ, indicating greater subjective cognitive complaints (estimate = 0.178, SE = 0.0821, p = 0.033). Greater entorhinal tau SUVR corresponded to an attenuated increase in CFQ over time (estimate = -0.064, SE = 0.0296, p = 0.035), whereas greater hippocampal tau SUVR was associated with a steeper longitudinal decline in memory (estimate = -0.0293, SE = 0.0135, p = 0.032).
Discussion
Individuals with higher levels of tau pathology may experience greater levels of subjective cognitive complaints. Such associations are detectable among cognitively normal individuals even in the absence of marked neuropathology-associated differences in neuropsychological assessments of verbal episodic memory, suggesting that subjective cognitive complaints may serve as early indicators of accumulating cerebral tau pathology.
