低密度脂蛋白(LDL)與中風之間的關係可能會被取代嗎??

研究：LDL並非總是預測中風風險最好的指標

作者：Caroline Cassels
出處：WebMD醫學新聞

　 　December 27, 2007 —一項由加州大學洛杉磯分校醫學中心研究者進行的研究顯示，三酸甘油酯最高的個體，其發生LAA的機會高出2.7倍，而那些非HDL濃度最高的個體，發生大血管中風風險高出2.5倍；三酸甘油酯與非高密度脂蛋白（HDL）濃度上升，與大血管粥狀硬化（LAA）有關，暗示低密度脂蛋白（LDL）可能並非總是動脈硬化血管風險最好的指標。
　　
　　主要研究者Bruce Ovbiagele醫師在美國神經學會的聲明中表示，LDL已經是降低中風風險的主要標的，但是這些結果顯示其他種類的膽固醇與中風風險的關係更為強烈。
　　
　　這項研究結果於12月26日發表於神經學期刊上。
　　
　　【衝突的證據】
　　根據作者表示，有關於循環中血脂肪對於中風風險的影響，證據是衝突的，部分早期的研究結果顯示，中風風險與膽固醇濃度上升無關；然而，他們表示，這項研究一般並未區分中風形式或是血脂肪的形式。
　　
　　近來的研究已經證實血脂肪濃度與缺血性中風之間的關係，但很少有研究檢驗血脂肪與跟脂肪代謝最相關之不同缺血性中風亞型之間的關係。
　　
　　他們寫道，這對血脂肪濃度在腦血管粥狀硬化形成上可能與冠狀動脈血管床不同的證據上是很重要的。
　　
　　作者指出，目前的美國國家治療指引強調處理LDL膽固醇，大部分是根據來自心臟相關研究的證據；然而，他們表示，有越來越多的證據顯示，其他來自典型血脂肪的不同血脂肪，可能是比LDL在預測血管風險上更好的預測因子。
　　
　　【大型研究】
　　在這項研究中，研究者針對1,049位在2002年9月到2007年4月之間，因為急性中風或是短暫性缺血性發作住進一家大學醫院醫學中心的病患，分析常規監測血脂肪濃度以及發生LAA中風之間的關係。
　　
　　所有病患都在入院後的早晨檢驗空腹血脂肪濃度，檢驗總膽固醇、三酸甘油酯、HDL與LDL；除此之外，也評估非HDL膽固醇、總膽固醇對HDL比值、三酸甘油酯對HDL比值、以及LDL對HDL比值。
　　
　　根據他們的臨床症候群、磁振擴散權重影像數據、以及血管、心臟與實驗室數值的結果，病患被分為兩群，分別是LAA與非LAA。
　　
　　整體而言，247位LAA組病患，以及802位病患被歸類為非LAA組；非LAA組包括395位心因性栓塞病患、224位小血管疾病（SVD）中風病患、89位其他已確認病因病患、以及94位原因不明中風。
　　
　　【LDL的價值不應該打折扣】
　　研究顯示，LAA與SVD病患的血脂肪濃度並無差異；此外，總膽固醇、三酸甘油酯、LDL、非HDL、三酸甘油酯對HDL比值，LAA組病患顯然比非LAA與非SVD病患高。
　　
　　在校正年齡、高血壓、糖尿病與是否有吸菸習慣、身體質量指數、以及在症狀發生前是否曾使用statins類藥物後，研究者發現三酸甘油酯與非HDL與LAA之間有強烈關係；然而，LAA與LDL之間並無關聯。
　　
　　作者指出，其數據顯示，其他傳統血清脂肪，例如三酸甘油酯濃度以及常規血脂肪檢驗較少量測的，例如非HDL膽固醇，可能與有症狀大血管脊腦部血管動脈硬化（相較於其他缺血性中風亞型）的關係更強。
　　
　　根據這些研究結果，作者表示，當治療有粥狀動脈血管硬化中風風險或處於風險的病患，臨床醫師可能需要將更多的注意力放在其他的血脂肪；然而，他們也表示，LDL與病患整體健康的重要性不應該打折扣。
　　
　　作者表示無相關資金上的往來。

LDL Not Always Best Predictor of Stroke Risk, Study Finds

By Caroline Cassels
Medscape Medical News

December 27, 2007 — Elevated levels of serum triglycerides and non–high-density lipoprotein (HDL) have been associated with an increased risk of large artery atherosclerotic (LAA) stroke, suggesting that low-density lipoprotein (LDL) may not always be the best predictor of atherosclerotic vascular risk.

A study by investigators at the University of California, Los Angeles Medical Center shows that individuals with the highest triglycerides are 2.7 times more likely to have LAA, while those with the greatest non-HDL levels had a 2.4-fold increased risk of large artery stroke.

"LDL has been the primary target for reducing the risk of stroke, but these results show other types of cholesterol may be more strongly linked with stroke risk," principal investigator Bruce Ovbiagele, MD, said in a statement from the American Academy of Neurology.

The study is published online December 26 in Neurology.

Conflicting Evidence

According to the authors, there is conflicting evidence with respect to the importance of circulating serum lipids in stroke, with some early studies reporting no association between stroke risk and elevated cholesterol. However, they note, this research generally did not distinguish between stroke subtype or lipid subfractions.

More recent studies have demonstrated an association between serum cholesterol levels and ischemic stroke, but few have examined the relationship between serum lipids and subtype of ischemic stroke most directly linked to lipid metabolism.

"This may be important in light of evidence that the effect of plasma lipids on atherogenesis in the cerebral vascular bed may be distinct from that in the coronary vascular bed," they write.

The authors point out that current national US guidelines, which emphasize the management of LDL cholesterol, are largely based on evidence from the cardiac literature.

However, they note, "there is mounting evidence that other serum lipid indices derived from the classic lipid profile may be better predictors of vascular risk than LDL."

Large Study

For the study, the investigators analyzed measures of routinely ordered serum lipid panels and the occurrence of LAA stroke in 1049 patients admitted with acute stroke or transient ischemic attack from September 2002 through April 2007 to a single university center.

All patients had fasting lipid panels drawn early in the morning the day after hospital admission. Total cholesterol, triglycerides, HDL, and LDL were assessed. In addition, non-HDL cholesterol, total cholesterol-to-HDL ratio, triglyceride-to-HDL ratio, and LDL-to-HDL ratio were also assessed.

Based on their clinical syndromes, diffusion-weighted imaging data, and the results of vascular, cardiologic, and laboratory studies, patients were divided into 2 groups — LAA and non-LAA.

Overall, 247 patients were in the LAA group and 802 classified in the non-LAA group. The non-LAA group consisted of 395 patients with cardioembolism, 224 with small vessel disease (SVD) stroke, 89 patients with other determined etiology, and 94 patients with cryptogenic stroke.

LDL Should Not Be Discounted

The study showed lipid levels were similar between LAA and SVD patients. Furthermore, total cholesterol, triglycerides, LDL, non-HDL, and triglyceride/HDL ratio were significantly higher in LAA than in non-LAA, non-SVD patients.

After adjusting for age, hypertension, diabetes, smoking habits, body-mass index, and the prior use of statins before onset of symptoms, the investigators found a strong association between triglycerides and non-HDL and LAA. However, there was no association between LAA and LDL.

"Our data indicate that other traditional serum lipid measures such as the triglyceride level, as well as less commonly assessed indices derived from the routinely ordered serum lipid panel such as non-HDL cholesterol, may be more strongly associated with symptomatic large artery cervicocephalic atherosclerosis (vs all other ischemic stroke subtypes) than LDL level," the authors write.

In light of these findings, the authors suggest when treating patients with or at risk for atherosclerotic stroke, clinicians may want to consider focusing additional attention on other aspects of the lipid panel. However, they note, LDL and its role in patients' overall health should not be discounted.

The authors report no conflicts of interest.

Neurology. Published online December 26, 2007.