64 Chapter 4 4.1 ABSTRACT A previous study has shown that WMH shape is associated with long-term risk for dementia after 10 years in community-dwelling older adults. However, the exact association with decline in different cognitive domains remains unknown. The current study aimed to investigate the association of WMH shape and decline in three cognitive domains over 5 years’ time in community-dwelling older adults. The association of baseline WMH shape (solidity, convexity, concavity index, fractal dimension, and eccentricity) and cognitive decline over 5.2 ± 0.3 years (domains: memory, executive function, and processing speed) were investigated using linear regression models in the Age, Gene/Environment Susceptibility-Reykjavik (AGES) study (n = 2560). A more irregular shape of periventricular/confluent WMH was related to cognitive decline in the memory domain (lower solidity (B: -0.04 (95% CI: -0.07—-0.01); p=0.005), lower convexity (-0.07 (-0.10—-0.04); p<0.001), a higher concavity index (-0.09 (-0.12—- 0.06); p<0.001), and a higher fractal dimension (-0.07 (-0.10—-0.04); p<0.001)), the executive function domain (lower convexity ((-0.04 (-0.07—-0.01); p=0.009), a higher concavity index (-0.04 (-0.07—-0.01); p=0.003), and a higher fractal dimension (-0.04 (-0.07—-0.01); p=0.009)), and the processing speed domain (lower solidity (-0.04 (-0.07—-0.02); p<0.001), lower convexity (-0.06 (-0.08—-0.03); p<0.001), a higher concavity index (-0.08 (-0.10—-0.05); p<0.001), and higher fractal dimension (-0.06 (-0.09—-0.04); p<0.001)) over 5.2 years. No associations were found between deep WMH shape and cognitive decline in any of the cognitive domains. These findings show that WMH shape patterns may be indicative of relatively short-term cognitive decline in community-dwelling older adults. This supports the evidence of WMH shape being a valuable marker that may be used to assess and predict cognitive outcome related to cerebrovascular disease progression.
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