Rajan Kumar B, Wilson Robert S, Barnes Lisa L, Aggarwal Neelum T, Weuve Jennifer, Evans Denis A
Department of Internal Medicine, Rush Institute for Healthy Aging.
Rush Alzheimer's Disease Center.
J Gerontol A Biol Sci Med Sci. 2017 Mar 1;72(3):424-430. doi: 10.1093/gerona/glw246.
Cognitive changes during the preclinical phase of Alzheimer's disease (AD) dementia have been characterized among European Americans (EAs), but studies of preclinical changes among African Americans (AAs) are notably absent.
Preclinical changes in cognition before the development of AD dementia and mild cognitive impairment over a period of 18 years were examined using change points in a biracial sample of 2,125 older adults.
Of 2,125 participants, 442 (21%) developed AD dementia and 661 (31%) developed mild cognitive impairment. A cognitive change point occurred between 4 and 5 years before the clinical diagnosis of AD dementia. Differences between AAs and EAs were observed: EAs had a higher starting level of composite cognitive function, and a change point occurred 4.3 years before AD dementia among AAs and 4.7 years among EAs. The slope of cognitive decline after the change point among those developing clinical AD dementia was significantly greater among EAs (0.233 units/y) than among AAs (0.171 units/y; p < .001). This difference in slope of cognitive decline persisted after diagnosis of AD dementia so that at the conclusion of observation the difference in average cognitive level was reversed. AAs without cognitive impairment had a lower average baseline of cognition than EAs, but the slopes of cognitive decline were similar.
A prominent change to a steeper slope of cognitive decline occurs between 4 and 5 years prior to the diagnosis of AD dementia. The slope of cognitive decline after the change point is steeper among EAs than AAs.
阿尔茨海默病（AD）痴呆临床前期的认知变化在欧裔美国人（EA）中已有特征描述，但非裔美国人（AA）临床前期变化的研究明显缺乏。
在一个包含2125名老年人的双种族样本中，利用变化点研究了AD痴呆和轻度认知障碍发生前18年期间认知的临床前期变化。
在2125名参与者中，442人（21%）患AD痴呆，661人（31%）患轻度认知障碍。AD痴呆临床诊断前4至5年出现认知变化点。观察到AA和EA之间存在差异：EA的综合认知功能起始水平较高，AA在AD痴呆前4.3年出现变化点，EA在AD痴呆前4.7年出现变化点。在发展为临床AD痴呆的人群中，变化点后EA的认知衰退斜率（0.233单位/年）显著大于AA（0.171单位/年；p <.001）。AD痴呆诊断后，这种认知衰退斜率的差异仍然存在，因此在观察结束时，平均认知水平的差异发生了逆转。无认知障碍的AA的平均认知基线低于EA，但认知衰退斜率相似。
在AD痴呆诊断前4至5年，认知衰退斜率出现显著变化，变为更陡。变化点后，EA的认知衰退斜率比AA更陡。
