Table_4_Lagged Coupled Changes Between White Matter Microstructure and Processing Speed in Healthy Aging: A Longitudinal Investigation.pdf

Age-related differences in white matter (WM) microstructure have been linked to lower performance in tasks of processing speed in healthy older individuals. However, only few studies have examined this link in a longitudinal setting. These investigations have been limited to the correlation of simultaneous changes in WM microstructure and processing speed. Still little is known about the nature of age-related changes in WM microstructure, i.e., regionally distinct vs. global changes. In the present study, we addressed these open questions by exploring whether previous changes in WM microstructure were related to subsequent changes in processing speed: (a) 1 year later; or (b) 2 years later. Furthermore, we investigated whether age-related changes in WM microstructure were regionally specific or global. We used data from four occasions (covering 4 years) of the Longitudinal Healthy Aging Brain (LHAB) database project (N = 232; age range at baseline = 64–86). As a measure of WM microstructure, we used mean fractional anisotropy (FA) in 10 major WM tracts averaged across hemispheres. Processing speed was measured with four cognitive tasks. Statistical analyses were conducted with bivariate latent change score (LCS) models. We found, for the first time, evidence for lagged couplings between preceding changes in FA and subsequent changes in processing speed 2 years, but not 1 year later in some of the WM tracts (anterior thalamic radiation, superior longitudinal fasciculus). Our results supported the notion that FA changes were different between regional WM tracts rather than globally shared, with some tracts showing mean declines in FA, and others remaining relatively stable across 4 years.

年龄相关的脑白质（white matter, WM）微结构差异，已被证实与健康老年人的加工速度任务表现下降相关。然而，目前仅有少量研究在纵向研究框架下探讨了这一关联。此类研究仅局限于脑白质微结构与加工速度的同步变化之间的相关性分析。目前学界仍不清楚脑白质微结构年龄相关变化的本质，即究竟是区域特异性变化还是整体全局性变化。本研究旨在解决这些尚未明确的问题，探究脑白质微结构的前期变化是否与后续的加工速度变化相关：(a) 滞后1年；或(b) 滞后2年。此外，本研究还探讨了脑白质微结构的年龄相关变化究竟是区域特异性的，还是全局性的。本研究使用了纵向健康老化脑（Longitudinal Healthy Aging Brain, LHAB）数据库项目的4次随访数据（覆盖时长4年），共纳入232名受试者，基线年龄范围为64~86岁。本研究采用两侧大脑半球10条主要脑白质束的平均各向异性分数（fractional anisotropy, FA）作为脑白质微结构的量化指标。加工速度通过四项认知任务进行评估。统计分析采用双变量潜变量变化得分（bivariate latent change score, LCS）模型完成。本研究首次发现，在部分脑白质束（丘脑前辐射、上纵束）中，脑白质各向异性分数的前期变化与2年后的加工速度变化存在滞后关联，但并未发现1年后存在此类关联。研究结果支持以下观点：脑白质各向异性分数的变化存在脑区特异性，而非全局性一致的变化——部分脑白质束的各向异性分数呈现平均水平下降，而其余脑白质束在4年随访期内相对保持稳定。