據(jù)1月19日刊《美國醫(yī)學會雜志》上的一項研究披露，沒有癡呆癥的老年人,，如果其血漿中生物標記物β-淀粉樣物質42/40（蛋白碎片）的濃度較低,，其在一個為期9年的時間中的認知概念的衰退速度會增加,。研究人員還發(fā)現(xiàn)，在受教育較少及文化水平較低的人中,，這種相關性也較強,。
根據(jù)文章的背景資料，據(jù)估計,，目前患有癡呆癥的人多達3600萬,，其流行率預計會每20年增加一倍,。文章的作者寫道：“因此，如果這類干預及治療存在的話,，可辨識發(fā)生癡呆癥風險的老年人的生物標記物對癡呆癥的早期預防會有用,。血漿β-淀粉樣物質42和42/40濃度較低與癡呆癥發(fā)病率有關聯(lián)，但其結果存在著相互矛盾,，而且很少有研究對沒有癡呆癥的老年人的認知衰退進行過調查,。”
加州大學舊金山分校及舊金山退伍軍人事務醫(yī)療中心的Kristine Yaffe, M.D.及其同僚開展了一項研究，旨在調查在一大群的社區(qū)居住的沒有癡呆癥的老年人中,，他們的血漿β-淀粉樣物質42與42/40的濃度與認知功能衰退之間的關系；同時受到調查的還有,，認知儲備量（以所獲得的教育水平和文化程度作為標志）是否會改變血漿β-淀粉樣物質的濃度與認知衰退之間的相關性,。
研究人員發(fā)現(xiàn)，在為期9年的時間中,，β-淀粉樣物質42/40濃度低與較大的認知功能衰退之間有關聯(lián),。在對幾種因子進行校正之后，這些結果仍然具有統(tǒng)計學上的顯著性,。在血漿β-淀粉樣物質42濃度與認知功能衰退之間也存在著顯著的相關性,。在血漿β-淀粉樣物質40濃度和基線認知功能或其衰退之間則沒有相關性。
另外,，認知功能儲備量可修飾β-淀粉樣物質42/40濃度與認知功能衰退之間的相關性,。該儲備量低的老年人（表現(xiàn)為低于高中文憑或6年級或較低的文化水平）的β-淀粉樣物質42/40濃度與認知功能衰退之間具有更大的相關性，相反,，在那些儲備量高的人中,，這種相關性則較小。
文章的作者寫道：“這些結果非常重要,，因為認知損害的流行率正呈現(xiàn)指數(shù)性地增加,，而預防措施將是關鍵性的。為了發(fā)現(xiàn)那些有罹患癡呆癥風險的人,，像血漿β-淀粉樣物質濃度這樣的相對容易獲得而且創(chuàng)傷性極小的生物標記物可能是有用的,。另外，我們發(fā)現(xiàn)的在認知儲備與血漿β-淀粉樣物質濃度和認知功能衰退之間的相關性可能具有公共衛(wèi)生方面的重要性,，因為它可能提示存在著諸如與認知活動或正在進行的教育等可改變β-淀粉樣物質對認知功能影響的途徑,。”
“未來的研究應該進一步地探索血漿β-淀粉樣物質作為一種生物標記物的應用，對認知儲備改變這一關系的機制進行評估,，并確定通過相互作用來增加認知儲備等干預手段是否可以減少阿茲海默病的風險”（生物谷Bioon.com）
生物谷推薦原文出處：
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.
