Tau positron emission tomography (PET) provides the most consistent predictive value for cognitive decline in cognitively normal and cognitively impaired adults compared with other commonly used biomarkers, according to a study published in Neurology.
Middle-aged and older adult volunteers who participated in the Adult Children Study and the Healthy Aging and Senile Dementia studies were included in the analysis (n=152). Participants had ≥1 tau PET scan, ≥1 amyloid PET scan, and structural magnetic resonance imaging with ≥2 clinical and cognitive evaluations available for review. Investigators evaluated cognition with measures reflecting executive function, episodic memory, semantic fluency, and processing speed on an annual basis.
Cognitive change was associated with amyloid PET (model 2; β = −0.010, P =.010), tau PET (model 3; β = -0.024; P <.001), and neurodegeneration (model 4; β = 0.012; P =.006) when modeled for age, sex, Clinical Dementia Rating score, and years of education. In a combined model, tau PET was the only biomarker significantly associated with cognitive change (model 8; β = −0.022, P <.001).
A follow-up analysis for each cognitive test was performed. Similar to the initial analysis, only tau PET was associated with substantial changes on Free and Cued Selective Reminding Test (β = −0.050; P <.0001) total free recall and Trail Making B (β = 0.051; P <.001). No association was found, however, between tau PET and Trail Making A (β = 0.003; P =.747) or Animal Naming (β = −0.010; P =.442).
Limitations of the study include its retrospective analysis of cognitive functioning as well as the relatively small sample size.
“These findings are consistent with the notion that tau accumulation is a primary determinant of cognitive decline and support the utility of tau PET imaging in assessing Alzheimer’s disease-related cognitive change,” the investigators concluded.
Aschenbrenner AJ, Gordon BA, Benzinger TLS, Morris JC, Hassenstab JJ. Influence of tau PET, amyloid PET, and hippocampal volume on cognition in Alzheimer disease. Neurology. 2018; 91:e859-e866.