Stable individual differences dominate adult brain volume variation until later life

Area of Science:

• Neuroscience
• Aging Research
• Biostatistics

Background:

• Individual differences in brain structure volumes are linked to neurological conditions and overall brain health.
• The extent to which these differences stem from early adulthood stability versus later-life aging trajectories remains unclear.

Purpose of the Study:

• To analyze the aging dynamics of six brain structure volumes in a large, cross-cohort longitudinal sample.
• To differentiate the contributions of stable early-life levels versus age-related changes to volumetric variance across adulthood.

Main Methods:

• Utilized magnetic resonance imaging (MRI) scans from 8,311 cognitively healthy adults (ages 18-97).
• Applied a stochastic dynamical model to estimate variability and persistence of structural brain changes.
• Calculated the proportion of variance attributable to stable levels versus rate-of-change differences.

Main Results:

• Before age 60, inter-individual brain volume differences are primarily due to stable individual levels.
• After age 60, differences in aging trajectories account for up to 50% of volumetric variation.
• Ventricular volume differences are linked to early adulthood changes; current brain-age models lack sensitivity to detect trajectory differences.

Conclusions:

• Distinguishing stable early adulthood brain volumes from systematic age-related changes is crucial for understanding adult brain aging.
• Reliability of imaging studies in detecting inter-individual brain changes increases significantly after age 60.