Aβ-Positivity Predicts Cognitive Decline but Cognition Also Predicts Progression to Aβ-Positivity
IntroductionBiomarker positivity predicts cognitive decline and Alzheimers dementia. But what predicts biomarker positivity? We hypothesized that cognitive function and p-tau would predict progression from normal to abnormal levels of {beta}-amyloid (A{beta}). MethodsBaseline cognition in 292 non-demented, A{beta}-negative Alzheimers Disease Neuroimaging Initiative (ADNI) participants was measured with two cognitive composites and compared between those that progressed to A{beta}-positivity versus A{beta}-stable. Follow-up analyses included continuous CSF A{beta} and p-tau levels to examine subthreshold effects. ResultsContinuously measured baseline subthreshold A{beta} and p-tau predicted progression to A{beta}-positivity, but both baseline cognitive measures predicted progression to A{beta}-positivity even after controlling for baseline biomarker levels. DiscussionCurrent A{beta} thresholds may be ignoring relevant subthreshold pathology. Importantly, cognitive function can be an important early predictor of future risk, even earlier than the key biomarkers as currently measured. Moreover, A-/T+ individuals may still be on the AD pathway because p-tau also predicted progression to positivity.