Relationship between baseline plasma p‐tau181 and longitudinal changes in cognition and structural brain measures in a cohort of cognitively unimpaired older adults

INTRODUCTION: Preclinical Alzheimer's disease (AD) affects a significant proportion of cognitively unimpaired (CU) older adults. Currently, blood‐based biomarkers detect very early changes in the AD continuum with great accuracy. METHODS: We measured baseline plasma phosphorylated tau (p‐tau)181 using electrochemiluminescence (ECL)‐based assay (MesoScale Discovery) in 533 CU older adults. Follow‐up lasted up to 18 months. Cognitive performance assessment included memory and cognitive control. Structural brain measures included cortical thickness, which includes the AD magnetic resonance imaging (AD MRI) signature, and hippocampal volume. RESULTS: In this cohort of CU older adults, baseline plasma p‐tau181 levels were not associated with short‐term changes in cognition and structural brain measures. Also, baseline plasma p‐tau levels did not influence the effects of behavioral interventions (exercise or mindfulness) on cognitive and structural brain changes. DISCUSSION: The short follow‐up and healthy status of this CU cohort might have limited the sensitivity of plasma p‐tau181 in detecting changes associated with AD pathology.