Impact of amyloid and tau positivity on longitudinal brain atrophy in cognitively normal individuals

Abstract

Background: Individuals on the preclinical Alzheimer's continuum, particularly those with both amyloid and tau positivity (A + T +), display a rapid cognitive decline and elevated disease progression risk. However, limited studies exist on brain atrophy trajectories within this continuum over extended periods. Methods: This study involved 367 ADNI participants grouped based on combinations of amyloid and tau statuses determined through cerebrospinal fluid tests. Using longitudinal MRI scans, brain atrophy was determined according to the whole brain, lateral ventricle, and hippocampal volumes and cortical thickness in AD-signature regions. Cognitive performance was evaluated with the Preclinical Alzheimer's Cognitive Composite (PACC). A generalized linear mixed-effects model was used to examine group × time interactions for these measures. In addition, progression risks to mild cognitive impairment (MCI) or dementia were compared among the groups using Cox proportional hazards models. Results: A total of 367 participants (48 A + T +, 86 A + T −, 63 A − T +, and 170 A − T − ; mean age 73.8 years, mean follow-up 5.1 years, and 47.4% men) were included. For the lateral ventricle and PACC score, the A + T − and A + T + groups demonstrated statistically significantly greater volume expansion and cognitive decline over time than the A − T − group (lateral ventricle: β = 0.757 cm3/year [95% confidence interval 0.463 to 1.050], P