據(jù)1月19日刊《美國醫(yī)學(xué)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(zhì)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(guān)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(yù)計會每20年增加一倍。文章的作者寫道：“因此,，如果這類干預(yù)及治療存在的話,，可辨識發(fā)生癡呆癥風(fēng)險的老年人的生物標記物對癡呆癥的早期預(yù)防會有用。血漿β-淀粉樣物質(zhì)42和42/40濃度較低與癡呆癥發(fā)病率有關(guān)聯(lián),，但其結(jié)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(diào)查。”
加州大學(xué)舊金山分校及舊金山退伍軍人事務(wù)醫(yī)療中心的Kristine Yaffe, M.D.及其同僚開展了一項研究,，旨在調(diào)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(zhì)42與42/40的濃度與認知功能衰退之間的關(guān)系；同時受到調(diào)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(zhì)的濃度與認知衰退之間的相關(guān)性,。
研究人員發(fā)現(xiàn),，在為期9年的時間中，β-淀粉樣物質(zhì)42/40濃度低與較大的認知功能衰退之間有關(guān)聯(lián),。在對幾種因子進行校正之后,，這些結(jié)果仍然具有統(tǒng)計學(xué)上的顯著性。在血漿β-淀粉樣物質(zhì)42濃度與認知功能衰退之間也存在著顯著的相關(guān)性,。在血漿β-淀粉樣物質(zhì)40濃度和基線認知功能或其衰退之間則沒有相關(guān)性,。
另外，認知功能儲備量可修飾β-淀粉樣物質(zhì)42/40濃度與認知功能衰退之間的相關(guān)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(zhì)42/40濃度與認知功能衰退之間具有更大的相關(guān)性,，相反，在那些儲備量高的人中,，這種相關(guān)性則較小,。
文章的作者寫道：“這些結(jié)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(yù)防措施將是關(guān)鍵性的,。為了發(fā)現(xiàn)那些有罹患癡呆癥風(fēng)險的人，像血漿β-淀粉樣物質(zhì)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(zhì)濃度和認知功能衰退之間的相關(guān)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(zhì)對認知功能影響的途徑,。”
“未來的研究應(yīng)該進一步地探索血漿β-淀粉樣物質(zhì)作為一種生物標記物的應(yīng)用,，對認知儲備改變這一關(guān)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(yù)手段是否可以減少阿茲海默病的風(fēng)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.
