White matter microstructural integrity and cognitive function in a general elderly population.
BACKGROUND
The role of macrostructural white matter changes, such as atrophy and white matter lesions, in cognitive decline is increasingly being recognized. However, in the elderly population, these macrostructural changes do not account for all variability in cognition. Measures reflecting white matter microstructural integrity may provide additional information to investigate the relation between white matter changes and cognition.


OBJECTIVE
To study the relation between white matter integrity and cognition in the general elderly population, using diffusion tensor imaging and taking into account macrostructural white matter changes.


METHODS
Cross-sectional population-based study.


METHODS
A general community in the Netherlands.


METHODS
A population-based sample of 860 persons, older than 60 years, free of dementia. We performed multisequence magnetic resonance imaging, which included diffusion tensor imaging, and extensive neuropsychological testing. Fractional anisotropy, mean diffusivity, and directional diffusivities were measured globally in white matter lesions and normal-appearing white matter.


METHODS
Performance on neuropsychological tests in the following cognitive domains: memory, executive function, information processing speed, global cognition, and motor speed.


RESULTS
Regardless of macrostructural white matter changes, a higher mean diffusivity or higher axial and radial diffusivities within white matter lesions or normal-appearing white matter were related to worse performance on tasks assessing information processing speed and global cognition. In addition, diffusivity within white matter lesions related to memory, while in normal-appearing white matter, it furthermore related to executive function. Lower mean fractional anisotropy in white matter lesions or normal-appearing white matter related to worse information processing speed and motor speed.


CONCLUSIONS
Microstructural integrity of both white matter lesions and normal-appearing white matter is associated with cognitive function, regardless of white matter atrophy and white matter lesion volume. This suggests that measuring white matter integrity has added value beyond macrostructural assessment of white matter changes to study the relation between white matter and cognition.
Department of Epidemiology, Erasmus MC University Medical Center, Rotterdam, the Netherlands.
Meike W
MW
Vernooij
M Arfan
MA
Ikram
Henri A
HA
Vrooman
Piotr A
PA
Wielopolski
Gabriel P
GP
Krestin
Albert
A
Hofman
Wiro J
WJ
Niessen
Aad
A
Van der Lugt
Monique M B
MM
Breteler
D000368:Aged; D000369:Aged, 80 and over; D001284:Atrophy; D001921:Brain / Q000473:pathology*; D003072:Cognition Disorders / Q000473:pathology*; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D009413:Nerve Fibers, Myelinated / Q000473:pathology*; D009426:Netherlands; D019636:Neurodegenerative Diseases / Q000473:pathology*; D009483:Neuropsychological Tests / Q000706:statistics & numerical data*; D009929:Organ Size / Q000502:physiology; D011594:Psychometrics; D012016:Reference Values; D013702:Temporal Lobe / Q000473:pathology