White matter trajectories over the lifespan.

Area of Science:

• Neuroscience
• Developmental Biology
• Radiology

Background:

• White matter (WM) undergoes significant changes throughout human development and aging.
• Understanding these age-related WM alterations is crucial for diagnosing neurological disorders and assessing brain health.

Purpose of the Study:

• To investigate age-related changes in white matter (WM) macro- and microstructural properties across the entire lifespan.
• To model the trajectories of these changes using various mathematical functions.
• To explore the influence of biological sex and hemispheric differences on WM development.

Main Methods:

• Aggregated 10,879 structural and 6,186 diffusion-weighted MRI scans from individuals aged 2 weeks to 100 years.
• Analyzed brain-wide and tract-specific WM partial volumes and microstructural properties (FA, MD).
• Fitted linear, quadratic, cubic, and exponential models to characterize age-related WM changes.

Main Results:

• WM volume increases steeply in infancy/childhood, then slows in adulthood and declines with aging.
• Microstructural properties like fractional anisotropy (FA) and mean diffusivity (MD) exhibit independent nonlinear trajectories across the lifespan.
• Age-related WM changes, including FA increase and MD decrease, show sex and hemispheric modulations, particularly in association tracts.

Conclusions:

• White matter macro- and microstructural changes follow nonlinear, age-dependent trajectories throughout life.
• Exponential changes characterize early-life WM development (first five years) for volume, FA, and MD.
• This lifespan approach offers novel insights into dynamic WM alterations and their influencing factors.