Baseline white matter microstructural integrity is not related to cognitive decline after 5 years: The RUN DMC study

OBJECTIVES: Traditional markers of cerebral small vessel disease (SVD) are related to cognition and cognitive decline, but this relation is weak. Therefore other factors may determine the transition from intact cognitive performance to cognitive decline, such as the damage of the cerebral white matter at the microstructural level. Little is known about the association between microstructural integrity of the white matter and changes in cognition. In this study we investigated the relation between baseline microstructural integrity and change in cognitive function. METHODS: 503 participants of the RUN DMC study with SVD without dementia, 398 of whom (79.1%) underwent repeated cognitive testing at follow-up, with a mean follow-up time of 5.4 years (± SD 0.2), and among others FLAIR MRI and diffusion tensor imaging (DTI). At baseline Mean Diffusivity (MD) and mean Fractional Anisotropy (FA) were measured in both white matter hyperintensities (WMH) and normal appearing white matter (NAWM). A linear regression analysis was performed assessing the association between baseline diffusion parameters and decline in cognitive domains. RESULTS: An inverse association was found between baseline MD in the NAWM and decline in Cognitive Index (β = 0.17; p = 0.035), adjusted for age, sex, education, presence of depressive symptoms at baseline, normalized TBV, lacunes and WMH volume. However, no significant associations were found between diffusion parameters and decline in any cognitive domain after Bonferroni correction. CONCLUSIONS: In contrast to cross-sectional studies, in older adults with SVD microstructural integrity of the white matter as assessed with DTI is not related to decline in global cognitive function or any other subdomain.