annana

作者：Caroline Cassels  
出處：WebMD醫學新聞

　　May 11, 2010 — 一篇跨世代、多中心研究認為，鐮刀型貧血症(Sickle cell anemia，SCA)與成人認知功能不佳有關聯，對於腦部的負面影響可能超過現有的知識。
　　
　　在首度探討認知功能和SCA成人的研究中，研究者發現，相較於健康對照組，此疾病與非語言功能低於平均值有關。
　　
　　SCA 病患在處理速度、操作記憶、整體認知功能和多數執行功能檢測的平均測驗分數也較低；SCA病患在有關視力掃描和注意力的檢測平均分數較低，顯示他們在選擇性注意上的困難。
　　
　　研究者認為，分數低於平均值的病患，在僱用、財務管理、藥物順從性、使用社區資源、社會功能等可能面臨挑戰。
　　
　　該研究發表於5月12日的美國醫療協會期刊(Journal of the American Medical Association)。
　　
　　【慢性成人疾病】
　　SCA曾經被視為高小兒死亡率的兒童期疾病，現在SCA病患的平均壽命超過50年，因此，SCA 成為與生活品質逐漸衰退有關的慢性疾病。
　　
　　加州奧克蘭兒童醫院暨研究中心的Elliott P. Vichinsky醫師等人寫道，對於這年齡層而言，神經認知功能不佳可能是最重要且最新的研究問題，就我們所知，未曾有成人病患的神經認知功能控制研究報告，孩童期之後也未進行例行性篩檢。
　　
　　研究者比較了在2004年12月至2008年5月間招募自美國12個醫學中心、有非洲SCA血統的149名19-55歲無神經症狀成人，和48名健康對照組的神經心理功能及神經學影像檢查結果。
　　
　　該研究的主要結果測量是「魏氏成人智力量表第三版、作業智商(Wechsler Adult Intelligence Scale, Third Edition [WAIS-III], Performance IQ [PIQ]Index)」評估的非口語功能。
　　
　　研究的次級結果包括執行功能、記憶、注意力、語言的神經認知檢測表現，此外，所有研究對象都接受磁振造影(MRI)，測量整體顱內與海馬迴容量、皮質灰質和白質和腔隙。
　　
　　【影像結果無法解釋表現差異】
　　校正年紀、性別、教育程度之後，研究者發現，SCA病患的非口語功能分數顯著低於對照組。WAIS-III PIQ分數低於正常平均值超過1個標準差(SD)的病患有33%，對照組則有15%，全國標準則預期是16%。
　　
　　SCA病患的所有次級結果平均分數也都較低，根據研究者指出，MRI結果並無法解釋表現上的差異，因為總體灰質或海馬迴容量並無差異。
　　
　　他們寫道，無神經症狀的成年SCA病患，依舊有神經認知表現不佳的風險，因為他們的貧血情況可能會導致次發於腦部低血氧的神經功能不佳，而標準神經影像檢查可能無法發現腦部低血氧。
　　
　　不過，他們指出，有許多方法可以嘗試用來減輕SCA對認知的影響，首先，及早以特定神經認知功能檢測確認有困難的病患，讓這些病患納入認知復健計畫並從中獲得幫助。
　　
　　研究作者們寫道，此外，必須進行縱向研究，以瞭解和評估疾病病程，這些研究可能和生物組成有關，以改善對SCA神經認知功能的瞭解。
　　
　　他們結論表示，探討輸血治療、神經保護劑、hydroxyurea、給予氧氣等治療方式改善此類病患之認知能力的介入研究也有其需要。
　　
　　費城大學的Samir K. Balas醫師在編輯評論中表示，該研究強調的事實是，SCA病患的神經認知不佳可能被忽視了，或者被視為適應不良的行為表現，而未被視為器質性惡化的結果。
　　
　　Balas醫師指出，對鐮刀型貧血症成人病患而言，標準與綜合的神經心理評估是一個有價值的評估工具。
　　
　　國家心臟、肺臟與血液研究中心支持本研究，研究作者與Balas醫師皆宣告沒有相關財務關係。


Sickle Cell Anemia Linked to Cognitive Dysfunction

By Caroline Cassels
Medscape Medical News

May 11, 2010 — Sickle cell anemia (SCA) has been linked to impaired cognitive function in adults and appears to have a much greater negative effect on the brain than previously thought, a cross-sectional, multicenter study suggests.

In the first study to examine cognitive functioning in adults with SCA, investigators found the disease was associated with lower than average nonverbal function scores compared with healthy controls.

SCA patients also had lower average scores for measures of processing speed, working memory, global cognitive function, and most measures of executive function. Difficulties with selective attention in SCA patients were illustrated by lower average scores for tests regarding visual scanning and attention.

The researchers suggest that patients with scores in the below average range may translate into challenges in difficulties with employment, financial management, medication adherence, use of community resources, and social functioning.

The study is published in the May 12 issue of the Journal of the American Medical Association.

Chronic Adult Illness

Once considered a childhood illness that was associated with high pediatric mortality, the average life span for patients with SCA now exceeds 50 years. As a result, SCA has become a chronic illness associated with progressive deterioration in quality of life.

"Neurocognitive dysfunction may be the most important and least studied problem affecting this aging population. To our knowledge, controlled studies of neurocognitive function in adult patients have not been reported and routine screening after childhood is not performed," researchers led by Elliott P. Vichinsky, MD, of Children's Hospital Research Center in Oakland, California, write.

The researchers compared neuropsychological function and neuroimaging findings between 149 neurologically asymptomatic adults aged 19 to 55 years of African descent with SCA recruited from 12 centers in the United States between December 2004 and May 2008 and 48 healthy matched controls from the community.

The study's primary outcome measure was nonverbal function assessed by the Wechsler Adult Intelligence Scale, Third Edition (WAIS-III), Performance IQ (PIQ) Index.

Secondary exploratory outcomes included performance on neurocognitive tests of executive function, memory, attention, and language. In addition, all participants underwent magnetic resonance imaging (MRI) measurement of total intracranial and hippocampal volume, cortical gray and white matter, and lacunae.

Imaging Findings Do Not Explain Performance Differences

After adjusting for age, sex, and education level, the investigators found SCA patients had statistically significant lower average nonverbal function scores than controls. The WAIS-III PIQ score was more than 1 SD below the normative average for 33% of patients and 15% of controls, compared with an expected 16% from the national norms.

SCA patients also had lower average scores on all secondary outcomes. According to investigators MRI findings did not explain performance differences because no differences in total gray matter or hippocampal volume were observed.

"Adult patients with SCA who are neurologically asymptomatic are still at risk for neurocognitive performance deficits because their anemia may be inducing neurocognitive impairment secondary to cerebral hypoxemia undetectable by standard neuroimaging studies," they write.

However, they add, several steps can be taken to try and mitigate the impact of SCA on cognition. "First, early identification of patients with difficulties on specific measures of neurocognitive function may allow these patients to enroll in, and benefit from, cognitive rehabilitation programs.

"Additionally, longitudinal studies are necessary to understand and evaluate disease progression. These studies can be linked to biological components to improve understanding of neurocognitive function in SCA," the study authors write.

They conclude that intervention studies testing treatments such as transfusion therapy, neuroprotective agents, hydroxyurea, and oxygenation and their ability to improve cognition in this patient population are needed.

In an accompanying editorial, Samir K. Balas, MD, Thomas Jefferson University in Philadelphia, Pennsylvania, says the study highlights the fact that "neurocognitive deficits may be overlooked in adult patients with SCA or discounted as a manifestation of maladaptive behavior rather than recognized as the result of an organic process."

Dr. Balas adds that standardized and comprehensive neuropsychological assessment may be a valuable tool in managing adult patients with sickle cell disease.

The study was supported by the National Heart, Lung, and Blood Institute. The study authors and Dr. Balas have disclosed no relevant financial relationships.

JAMA. 2010;303:1823-1831, 1862-1863.