作者：Pauline Anderson
出處：WebMD醫學新聞
October 16, 2008 — 一篇新研究發現，相較於對心血管系統的正面效果，酒精無法延緩年紀相關的腦容量衰退。
這些最新結果來自Framingham子代研究，研究發現衰退的腦容量與增加飲酒量之間的負面線性關係，且女性比男性更明顯。
不過，研究者衛斯理學院與波士頓大學公共衛生學院的Carol Ann Paul表示，這還不足以對大眾提出酒精對腦部之影響的警告。
Paul向 Medscape Psychiatry 表示，目前她還沒準備好詮釋這些資料的意義，或者提出任何有關改變飲酒量的建議；她指出，有一件事情是，研究中，與酒精相關的腦容量減少並不是很明顯，需要進行前溯縱向分析來確認這些結果。
這項研究登載於10月的神經學檔案期刊。
【飲酒量分類】
研究包括1,839名Framingham 子代研究這項1948年開始的縱向研究之研究對象的健康後代，這些後代在1991至2001年間被要求參加目前的這個分析，當時，這些人的年紀介於33至88歲之間。
研究對象報告他們每週飲酒量(啤酒、白酒紅酒與烈酒)，飲酒量分成四類：未曾飲酒者、曾經飲酒者、低度(1- 7份)、適度(8-14份)、高度(超過14份)。
研究者使用多變項線性回歸模式分析飲酒量與腦容量(利用磁振造影[MRI]測得)，校正年紀、性別、教育與其他因素。
對於曾經飲酒者，研究者沒有蒐集他們滴酒不沾的時間有多久、或者為何停止飲酒的資訊。
之前的研究顯示，適度飲酒— 或許每天一杯紅酒 — 可以預防心血管疾病；適度飲酒也可改善認知功能，降低阿茲海默氏症風險，與較少嚴重的白質病灶。
已知腦容量每年約自然衰退0.19%，或者每10年約2%，而白質病灶隨著年紀增加。
【希望找到和心臟類似的趨勢】
Paul表示，目前這個研究的目標，是希望確認酒精是否對腦容量有和對心臟一樣的好處，希望看到少量飲酒可以有減緩腦容積衰退的效果，就像對心臟一樣。
Paul表示，從心血管系統輸注大量血液到腦部，所以假設這些每天適度飲酒情況下的相同血液應該會有一樣的好處；擴大血管且清除一些東西。
不過，她發現的剛好相反；Paul表示，飲酒量越多，腦容積衰退越多。飲酒量和腦容積之間有明顯的負向線性關係。
在每組之間，換算成腦容量每年至少比正常老化多衰退平均0.25%。
Paul解釋，這表示飲酒對於血管的正面效果無法為腦部帶來一樣的效果，腦部細胞和腦血管所受到的影響似乎不一樣。
研究者未發現酒和白質病灶間的關係；以前的研究曾經指出，較大的白質病灶和較低的腦容量，失智惡化及認知衰退與較高的心血管風險有關。
【女性衰退更多】
雖然適度飲酒的男性比女性多，重度飲酒的男性是女性的兩倍，每個飲酒量類別中，女性的腦容積衰退比男性明顯。
Paul表示，女性的相關腦容積比男性多，但是酒並沒有比較多的效果；換句話說，趨勢一樣，但她們的負面衰退線略為陡峭。
Paul 指出，婦女體型一般比男性小，可稀釋飲酒的血液也較少，因此比較容易有這種結果。
該研究根據自我報告的飲酒量，因為人們往往會少報飲酒量，喝酒和腦容積之間的關係可能比研究所發現的還要大。
此外，研究對象大多數為歐洲血統者，且教育程度相對較高，所以作者表示，研究結果無法推論到其他種族和不同經濟族群。
Paul表示，下一步驟是比較同樣飲酒模式與認知之間的關係。
研究未宣告財經關係。
Framingham: Alcohol May Protect the Heart, But Not the Brain
By Pauline Anderson
Medscape Medical News
October 16, 2008 — In contrast to its observed positive effects on the cardiovascular system, alcohol does not slow age-related decline in brain volume, a new study has found.
These latest results, from the Framingham Offspring Study, found a negative linear line connecting decreased brain volume with increased alcohol consumption, with that line being more dramatic in women than in men.
However, according to study investigator Carol Ann Paul, from Wellesley College and Boston University School of Public Health, in Massachusetts, it would be premature to warn the public about this impact of alcohol on the brain.
Paul told Medscape Psychiatry that at this point she is not ready to speculate on the meaning of the data or make any recommendations regarding changes to alcohol consumption.
For one thing, she said, the brain shrinkage linked to alcohol in the study "is not tremendous," and more research in the form of prospective longitudinal analyses is needed to verify the results.
The study is published in the October issue of Archives of Neurology.
Alcohol Consumption Categorized
The study included 1839 healthy offspring of the original subjects of the Framingham Heart Study, a longitudinal study launched in 1948. The offspring were asked between 1991 and 2001 to participate in this current analysis. At the time, the offspring sample ranged in age from 33 to 88 years.
Subjects reported on their weekly alcohol consumption (beer, white and red wine, and liquor). Consumption was divided into five categories: abstainers, former drinkers, low (1 to 7 drinks, the majority), moderate (8 to 14 drinks), and high (more than 14 drinks).
Researchers used multivariate linear regression models to evaluate the association between these levels of alcohol consumption and brain volume as measured using magnetic resonance imaging (MRI), adjusting for age, sex, education, and other factors.
For former drinkers, researchers did not collect information on how long they had been "dry" or why or how they had stopped drinking.
Previous research has shown that moderate alcohol consumption — perhaps a glass of wine a day — may protect against cardiovascular disease. Moderate alcohol consumption is also associated with improved cognitive function, a lower risk for Alzheimer's disease, and less severe white-matter lesions.
It is also known that brain volume declines naturally at about 0.19% per year, or almost 2% per decade, while white-matter lesions increase with age.
Hoped to See Trend Similar to Heart
The goal going into this current study was to determine whether alcohol has the same protective effect on brain volume as it has on the heart, said Paul. "I was hoping to see some sort of reduction in [brain volume] decline with a small amount of alcohol, the same trend seen with the heart.
"The brain is heavily perfused with blood from the cardiovascular system, so the hypothesis was that those same blood vessels must be getting the same advantage of drinking alcohol every day; it dilates the blood vessels and sort of flushes things out," said Paul.
She found the opposite, however; the more a group of subjects drank, the larger their decline in brain volume. "There was a significant negative linear trend between the alcohol-consumption groups and brain volume," said Paul.
Between every group, there was a decline in brain volume of, on average, 0.25%, which translates into at least a 1-year additional decline in brain volume than would be expected with normal aging.
Paul interprets this to mean that alcohol's positive effect on blood vessels does not translate into the same effect elsewhere in the brain. "It seems that the cells of the brain are differently affected than the blood vessels of the brain."
The researchers did not find an association between alcohol and white-matter lesions. Past research has noted larger white-matter lesions and lower brain volume associated with the progression of dementia and cognitive decline as well as higher cardiovascular risk.
Decline More Pronounced In Women
Although there were more men than women in the moderate drinking category and twice as many in the heavy drinking group, the decline in brain volume was more pronounced among women in every alcohol-consumption category.
"Women have higher relative brain volume than men, but alcohol has more of an effect on them," said Paul. "In other words, the trend is in the same direction but their [negative decreasing] line is slightly steeper."
Paul pointed out that women are generally smaller than men, have less blood to dilute the alcohol they drink, and are more vulnerable to its effects.
The study was based on self-reports of alcohol consumption, and since people tend to underreport their use of alcohol, the association between alcohol and brain volume may actually be even greater than that uncovered by the study.
In addition, the participants were predominantly of European descent with a relatively high level of education, so the authors caution that the results may not be generalized to other racial and economic groups.
The next step is to compare the same alcohol-consumption patterns of this sample with cognition, said Paul.
No financial disclosure was reported.
Arch Neurol. 2008;65:1363-1367. Abstract
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