Determinants of Brain Aging in the Brazilian Longitudinal Study of Adult Health: Study Design, Neuroimaging Protocol,...

The aim of the study was to describe the design, the neuroimaging protocol as well as the baseline characteristics of the participants from Brazilian Longitudinal Study of Adult Health (ELSA-Brasil), which will be part of an extensive investigation of the determinants of brain aging based on high-resolution neuroimaging 3T and 7T magnetic resonance imaging (MRI) conceptualized by the Ageing and Brain Working Study Group from ELSA-Brasil.

A representative sample of 2,165 participants (mean age = 60.3 [9.9] years, 55.5% female) for further neuroimaging and study with the protocol described here was selected from ELSA-Brasil. The criteria used for selection into this protocol were cognitive status and age in wave 3 (2017-2019), and participants were split into two subsamples: (1) a randomized sample of participants with <70 years at wave 3 (2017-2019) categorized in three groups based on their global cognitive trajectories from wave 1 to wave 3 - (1) below the average (z-score <-1, n = 620), (2) average (z-score = -1 to +1, n = 835), and (3) above-average performance (z-score >+1, n = 215); and (2) all participants with ≥70 years at wave 3 were classified as SuperAgers cases (n = 171) and their matched controls (n = 324) based on delayed memory (wave 3). Both samples will be scanned using a 3T MRI, and an additional 7T MRI exam will be conducted in the SuperAgers study to further evaluate brain connectivity. An extensive dataset of sociodemographic, lifestyle, cognitive, mental health, frailty, and other laboratory and clinical exams collected since the baseline of the main study will be considered as predictors of structural and functional patterns of brain aging. The main characteristics of participants and the MRI protocol are described here.

Among those under 70 years, the above-average group for cognition showed better cognitive and mental health scores than the other groups (most p values <0.001). Considering the elderly who were 70 years or older, SuperAgers showed higher scores for delayed recall memory, better global cognition, and verbal fluency than controls at wave 3 (all p values <0.001).

The ELSA-Brasil study will be a unique opportunity to unravel the determinants of brain aging in an admixed sample in Latin America.