Lagged Coupled Changes Between White Matter Microstructure and Processing Speed in Healthy Aging: A Longitudinal...

Area of Science:

• Neuroscience
• Gerontology
• Cognitive Science

Background:

• Age-related white matter (WM) microstructure decline is linked to reduced processing speed in healthy older adults.
• Longitudinal studies examining the relationship between WM microstructure and processing speed are limited.
• The nature of age-related WM changes (regional vs. global) remains unclear.

Purpose of the Study:

• To investigate whether preceding changes in WM microstructure predict subsequent processing speed changes.
• To determine if these relationships manifest at 1-year or 2-year lags.
• To ascertain whether age-related WM changes are regionally specific or global.

Main Methods:

• Utilized data from the Longitudinal Healthy Aging Brain (LHAB) project (N=232, baseline age 64-86) over 4 years.
• Measured WM microstructure using mean fractional anisotropy (FA) in 10 major WM tracts.
• Assessed processing speed using four cognitive tasks and analyzed data with bivariate latent change score (LCS) models.

Main Results:

• Found significant lagged couplings between prior FA changes and subsequent processing speed declines at a 2-year interval in specific WM tracts (anterior thalamic radiation, superior longitudinal fasciculus).
• No significant lagged effects were observed at the 1-year interval.
• Evidence suggests FA changes are regionally distinct across WM tracts, rather than globally uniform.

Conclusions:

• WM microstructure changes, particularly FA declines in specific tracts, precede and predict declines in processing speed in older adults.
• These findings highlight the regional specificity of age-related WM alterations.
• The study provides novel longitudinal evidence for a lagged relationship between WM integrity and cognitive processing speed.