据1月19日刊《美国医学会杂志》上的一项研究披露，没有痴呆症的老年人，如果其血浆中生物标记物β-淀粉样物质42/40（蛋白碎片）的浓度较低，其在一个为期9年的时间中的认知概念的衰退速度会增加。研究人员还发现，在受教育较少及文化水平较低的人中，这种相关性也较强。
根据文章的背景资料，据估计，目前患有痴呆症的人多达3600万，其流行率预计会每20年增加一倍。文章的作者写道：“因此，如果这类干预及治疗存在的话，可辨识发生痴呆症风险的老年人的生物标记物对痴呆症的早期预防会有用。血浆β-淀粉样物质42和42/40浓度较低与痴呆症发病率有关联，但其结果存在着相互矛盾，而且很少有研究对没有痴呆症的老年人的认知衰退进行过调查。”
加州大学旧金山分校及旧金山退伍军人事务医疗中心的Kristine Yaffe, M.D.及其同僚开展了一项研究，旨在调查在一大群的社区居住的没有痴呆症的老年人中，他们的血浆β-淀粉样物质42与42/40的浓度与认知功能衰退之间的关系；同时受到调查的还有，认知储备量（以所获得的教育水平和文化程度作为标志）是否会改变血浆β-淀粉样物质的浓度与认知衰退之间的相关性。
研究人员发现，在为期9年的时间中，β-淀粉样物质42/40浓度低与较大的认知功能衰退之间有关联。在对几种因子进行校正之后，这些结果仍然具有统计学上的显著性。在血浆β-淀粉样物质42浓度与认知功能衰退之间也存在着显著的相关性。在血浆β-淀粉样物质40浓度和基线认知功能或其衰退之间则没有相关性。
另外，认知功能储备量可修饰β-淀粉样物质42/40浓度与认知功能衰退之间的相关性。该储备量低的老年人（表现为低于高中文凭或6年级或较低的文化水平）的β-淀粉样物质42/40浓度与认知功能衰退之间具有更大的相关性，相反，在那些储备量高的人中，这种相关性则较小。
文章的作者写道：“这些结果非常重要，因为认知损害的流行率正呈现指数性地增加，而预防措施将是关键性的。为了发现那些有罹患痴呆症风险的人，像血浆β-淀粉样物质浓度这样的相对容易获得而且创伤性极小的生物标记物可能是有用的。另外，我们发现的在认知储备与血浆β-淀粉样物质浓度和认知功能衰退之间的相关性可能具有公共卫生方面的重要性，因为它可能提示存在着诸如与认知活动或正在进行的教育等可改变β-淀粉样物质对认知功能影响的途径。”
“未来的研究应该进一步地探索血浆β-淀粉样物质作为一种生物标记物的应用，对认知储备改变这一关系的机制进行评估，并确定通过相互作用来增加认知储备等干预手段是否可以减少阿兹海默病的风险”（生物谷Bioon.com）
生物谷推荐原文出处：
JAMA. 2011;305(3):261-266. doi: 10.1001/jama.2010.1995
Association of Plasma β-Amyloid Level and Cognitive Reserve With Subsequent
Cognitive Decline Kristine Yaffe, MD; Andrea Weston, MPH; Neill R. Graff-Radford, MBBCh; Suzanne Satterfield, MD, DrPh; Eleanor M. Simonsick, PhD; Steven G. Younkin, MD, PhD; Linda H. Younkin, PhD; Lewis Kuller, MD, DrPh; Hilsa N. Ayonayon, PhD; Jingzhong Ding, MD, PhD; Tamara B. Harris, MD, MS
AbstractContext Lower plasma β-amyloid 42 and 42/40 levels have been associated with incident dementia, but results are conflicting and few have investigated cognitive decline among elders without dementia.
Objective To determine if plasma β-amyloid is associated with cognitive decline and if this association is modified by measures of cognitive reserve.
Design, Setting, and Participants We studied 997 black and white community-dwelling older adults from Memphis, Tennessee, and Pittsburgh, Pennsylvania, who were enrolled in the Health ABC Study, a prospective observational study begun in 1997-1998 with 10-year follow-up in 2006-2007. Participant mean age was 74.0 (SD, 3.0) years; 55.2% (n = 550) were female; and 54.0% (n = 538) were black.
Main Outcome Measures Association of near-baseline plasma β-amyloid levels (42 and 42/40 measured in 2010) and repeatedly measured Modified Mini-Mental State Examination (3MS) results.
Results Low β-amyloid 42/40 level was associated with greater 9-year 3MS cognitive decline (lowest β-amyloid tertile: mean change in 3MS score, ?6.59 [95% confidence interval [CI], ?5.21 to ?7.67] points; middle tertile: ?6.16 [95% CI, ?4.92 to ?7.32] points; and highest tertile: ?3.60 [95% CI, ?2.27 to ?4.73] points; P < .001). Results were similar after multivariate adjustment for age, race, education, diabetes, smoking, and apolipoprotein E [APOE ] e4 status and after excluding the 72 participants with incident dementia. Measures of cognitive reserve modified this association whereby among those with high reserve (at least a high school diploma, higher than sixth-grade literacy, or no APOE e4 allele), β-amyloid 42/40 was less associated with multivariate adjusted 9-year decline. For example, among participants with less than a high school diploma, the 3MS score decline was ?8.94 (95% CI, ?6.94 to ?10.94) for the lowest tertile compared with ?4.45 (95% CI, ?2.31 to ?6.59) for the highest tertile, but for those with at least a high school diploma, 3MS score decline was ?4.60 (95% CI,?3.07 to ?6.13) for the lowest tertile and ?2.88 (95% CI,?1.41 to ?4.35) for the highest tertile (P = .004 for interaction). Interactions were also observed for literacy (P = .005) and for APOE e4 allele (P = .02).
Conclusion Lower plasma β-amyloid 42/40 is associated with greater cognitive decline among elderly persons without dementia over 9 years, and this association is stronger among those with low measures of cognitive reserve.
