本帖最後由 goodcat1111 於 2009-4-8 23:17 編輯
作者：Laurie Barclay, MD
出處：WebMD醫學新聞
February 24, 2009 — 根據一項發表於2月23日內科學誌的隨機分派、雙盲、安慰劑控制研究結果，每天攝取葉酸、維生素B6、與維生素B12顯然可以降低心臟疾病高風險女性的老化相關黃斑病變（AMD）。
麻州波士頓布萊根婦女醫院的William G. Christen博士及其來自女性抗氧化與葉酸心血管研究的同事們寫到，觀察性試驗結果指出，血中半胱胺酸濃度與AMD風險之間是有關係的，但是缺乏檢驗降低半胱胺酸濃度療法效果的隨機分派研究數據；我們的目的在檢驗一項使用葉酸、維生素B6與維生素B12的研究中，AMD的發生率。
這項試驗族群包括5,442位40歲以上擔任健康照護職務的女性，這些女性都罹患心血管疾病且有3個以上的心血管疾病危險因子，這些受試者中，5,205位在試驗前並未被診斷罹患AMD，且被收納到研究分析中。
所有受試者都被隨機分派接受合併葉酸（每天2.5毫克）、維生素B6（每天50毫克）、以及維生素B12（每天1毫克）或是安慰劑。試驗的主要終點為整體AMD件數，由自我通報與病歷記載AMD造成視力受損，視力剩下20/30或是更糟來確認，平均治療與後續追蹤為7.3年。
在後續追蹤時，合併組中發現55件AMD、安慰劑組中則有82件（相對風險為0.66；95%信賴區間為0.47-0.93；P=0.02）。對於視力顯著受損的AMD，兩組中分別有26與44件（相對風險為0.59；95%信賴區間為0.36-0.95；P=0.03）。
這項研究的限制包括無法確定AMD風險下降是否因為合併治療降低了半胱胺酸濃度，還是與半胱胺酸濃度無關。
研究作者寫到，這些來自心血管疾病高風險女性的隨機分派研究數據顯示，每日攝取葉酸、維生素B6、維生素B12可能降低AMD風險；因為目前並沒有被認可之早期預防AMD的方法，除了戒菸之外，這些發現對於臨床與公共衛生有重要的應用，且需要在其他男性與女性族群中確認。
國家心臟、肺臟與血液機構與國家眼科機構贊助這項研究。Cognis集團提供維生素E與安慰劑。BASF公司提供所有其他藥物與安慰劑。部分試驗作者表示與國家衛生研究院、哈佛大學（臨床營養研究中心機構）、DSM營養產品有限公司（羅氏藥廠）、阿斯特捷利康、必治妥、默克、諾華與BASF集團以及/或是Cognis集團有不同資金上的往來。
Folic Acid, B Vitamins May Reduce Risk for Age-Related Macular Degeneration
By Laurie Barclay, MD
Medscape Medical News
February 24, 2009 — Daily supplementation with folic acid, pyridoxine, and cyanocobalamin appears to lower the risk for age-related macular degeneration (AMD) in women at high risk for cardiovascular disease, according to the results of a randomized, double-blind, placebo-controlled trial reported in the February 23 issue of the Archives of Internal Medicine.
"Observational epidemiologic studies indicate a direct association between homocysteine concentration in the blood and the risk of...AMD, but randomized trial data to examine the effect of therapy to lower homocysteine levels in AMD are lacking," write William G. Christen, ScD, from Brigham and Women's Hospital, Harvard Medical School in Boston, Massachusetts, and colleagues from the Women's Antioxidant and Folic Acid Cardiovascular Study. "Our objective was to examine the incidence of AMD in a trial of combined folic acid, pyridoxine hydrochloride (vitamin B6), and cyanocobalamin (vitamin B12) therapy."
The study cohort consisted of 5442 female healthcare professionals 40 years or older with preexisting cardiovascular disease or 3 or more cardiovascular disease risk factors. Of these participants, 5205 did not have a diagnosis of AMD at baseline and were included in this analysis.
All participants were randomly assigned to receive combined supplementation with folic acid (2.5?mg/day), pyridoxine hydrochloride (50 mg/day), and cyanocobalamin (1 mg/day) or placebo. The primary endpoints of the study were total AMD, identified from self-report and confirmed by medical record evidence of an initial diagnosis after randomization, and visually significant AMD, defined as confirmed incident AMD causing visual impairment with visual acuity of 20/30 or worse. Average duration of treatment and follow-up was 7.3 years.
During follow-up, 55 cases of AMD were identified in the combination treatment group and 82 in the placebo group (relative risk, 0.66; 95% confidence interval, 0.47 - 0.93; P =.02). For visually significant AMD, there were 26 cases and 44 cases, respectively (relative risk, 0.59; 95% confidence interval, 0.36 - 0.95; P = .03).
Limitations of this study include inability to determine whether the reduced risk for AMD was caused by lowering of homocysteine levels by the combination treatment or was independent of lowered homocysteine levels.
"These randomized trial data from a large cohort of women at high risk of cardiovascular disease indicate that daily supplementation with folic acid, pyridoxine, and cyanocobalamin may reduce the risk of AMD," the study authors write. "Because there are currently no recognized means to prevent the early stages of AMD development other than avoidance of cigarette smoking, these findings could have important clinical and public health implications and need to be confirmed in other populations of men and women."
The National Heart, Lung, and Blood Institute and the National Eye Institute supported this study. Cognis Corporation provided vitamin E and its placebo. BASF Corporation provided all other agents and their placebos. Some of the study authors have disclosed various financial relationships with the National Institutes of Health, Harvard University (Clinical Nutrition Research Center), DSM Nutritional Products, Inc (Roche), AstraZeneca, Bristol-Myers Squibb Co, Merck and Co, Inc, Novartis, BASF Corporation, and/or Cognis Corporation.
Arch Intern Med. 2009;169:335-341. |
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