Abstract
Trajectories of age-related neurocognitive decline are not uniform, and are impacted by numerous environmental and physiological factors. Earlier life phases set the stage for later life neurocognitive function, with midlife marking a critical transition characterized by increasing variability in cognitive, affective, and physiological functioning. Despite its importance, this turbulent period remains underrepresented in open neuroimaging and phenotypic data resources. To address this gap, the Nathan Kline Institute - Rockland Sample (NKI-RS) initiative created the 'Mapping Interindividual Variation in the Aging Connectome' (MIVAC) substudy-an openly shared, multimodal dataset designed to map brain aging trajectories beginning in midlife and assess the influence of modifiable factors such as cardiorespiratory fitness. This longitudinal investigation includes 348 community-ascertained participants aged 38 to 71 years at baseline. Data collection incorporated deep phenotyping across cognitive, behavioral, medical, and cardiorespiratory fitness domains, along with multimodal neuroimaging (resting-state fMRI, diffusion MRI, morphometric MRI, and arterial spin labeling) and biospecimen collection. The protocol harmonizes with prior NKI-RS substudies while incorporating age-specific considerations for cognitive and neural aging. The full dataset is openly available.