本帖最後由 lsc0019 於 2009-9-15 23:39 編輯
作者：Caroline Cassels
出處：WebMD醫學新聞
August 28, 2009 — 根據一項研究結果指出，相較於正常體重個體，過重與肥胖個體的腦容積顯著較低。這個現象讓這些人們處於發生失智的風險之下，包括阿茲海默氏症。
一項新影像檢驗結果顯示，平均來說，相較於正常體重個體，肥胖體重個體的腦容積低了8%、過胖個體低了4%。
主要研究者來自加州洛杉磯UCLA醫學院神經影像實驗室的Paul M. Thompson博士在一項聲明中表示，那是組織大量流失，且這耗盡你的認知存量，使得你處於發生阿茲海默氏症與其他攻擊腦部疾病的風險。
這項研究於8月6日線上發表於人類腦部圖譜（Human Brain Mapping）期刊上。
【全世界的問題】
肥胖，廣為人知會增加心血管疾病的風險，包括糖尿病、高血壓與中風，這些疾病都會增加認知功能下降與失智的風險。然而，作者們指出，這些因子，特別是肥胖與第二型糖尿病，都與腦部萎縮的特定特徵有關。
作者們指出，世界各地目前有超過10億人過重、3億人肥胖。除此之外，70歲以上男性有40%、女性有45%是肥胖或罹患第二型糖尿病。
為了檢驗老年受試者的灰質與白質腦容積差異，研究者使用肌張量為基礎的型態計量法來檢驗94位老年受試者的灰質與白質腦容積差異，這些受試者在掃描後至少5年都是維持認知功能正常的。
研究者使用心血管健康研究（CHS）認知研究的受試者資料，這是CHS失智症研究的延續，該項研究從2002/2003年開始，目的是確認於1998/1999年正常與輕微認知功能受損受試者，失智與輕微認知功能受損的發生率。
為了定義體重分級，他們使用身體質量指數（BMI）。正常體重以BMI介於18.5-25.0 kg/m2定義；過重定義為BMI介於25-30 kg/m2，而肥胖定義為BMI大於30 kg/m2。如果符合任一疾病標準條件，受試者就會被歸類為罹患第二型糖尿病。
在所有研究樣本中，29位受試者體重正常、51位過重、14位肥胖。
【老化效應】
多變項迴歸分析顯示，BMI負向地與腦部萎縮有關，第二型糖尿病與空腹血漿胰島素濃度則與其無關。具體來說，研究者發現，體組織程度高與前葉、顳葉、扣帶迴前部、海馬迴、基底核的腦組織流失有關。
過重個體的基底核、放射冠、頂葉腦組織流失。作者們報告肥胖個體身體組織脂肪與腦部結構呈強烈地負相關，但是這個現象也發生在過重病患。
Thompson博士表示，肥胖者的腦部看起來比身材纖細者老了16歲，而過重的人們則是老了8歲。
試驗研究者賓州匹茲堡大學醫學院的Cyrus A. Raji醫師在一項聲明中表示，隨著像是第二型糖尿病和心臟疾病的健康問題風險上升，肥胖對你的腦部來說是很糟的。我們已經將這與腦部區域的萎縮相連，這些區域是阿茲海默氏症的標的。但是，那也代表運動、正確飲食與體重控制可以讓腦部隨著老化仍保持健康，且潛在可能降低阿茲海默氏症與其他失智的風險。
研究者們表示沒有相關資金上的往來。
Overweight and Obesity Linked to Lower Brain Volume
By Caroline Cassels
Medscape Medical News
August 28, 2009 — Overweight and obese individuals have significantly lower brain volume than their normal-weight counterparts, a finding researchers say puts these individuals at much greater risk for dementia, including Alzheimer's disease.
Results from a new imaging study reveal that, on average, obese subjects had 8% lower brain volume than normal-weight subjects and overweight subjects had 4% lower brain volume.
"That's a big loss of tissue and it depletes your cognitive reserves, putting you at much greater risk of Alzheimer's and other diseases that attack the brain," principal investigator Paul M. Thompson, PhD, from the Lab of Neuro Imaging, UCLA School of Medicine, in Los Angeles, California, said in a statement.
The study was published online August 6 in Human Brain Mapping.
Worldwide Problem
It is well known that obesity increases the risk for cardiovascular illness, including diabetes, hypertension, and stroke, all of which increase the risk for cognitive decline and dementia. However, the authors point out, it is not known whether these factors, specifically obesity and type?2 diabetes, are associated with specific patterns of brain atrophy.
The authors note that there are currently more than 1?billion overweight and 300?million obese individuals worldwide. In addition, 40% of men and 45% of women older than 70 years are either obese or have type?2 diabetes.
To examine gray- and white-matter volume differences in elderly subjects, the researchers used tensor-based morphometry to examine gray- and white-matter volume differences in 94 elderly subjects who remained cognitively normal for a minimum of 5 years after their scan.
Researchers used participants in the Cardiovascular Health Study (CHS) Cognition Study, a continuation of the CHS Dementia Study, which began in 2002/2003, to determine the incidence of dementia and mild cognitive impairment in a population of normal and mild cognitive-impairment-subjects identified in 1998/1999.
To define weight categories, they used the body mass index (BMI). Normal weight was defined as a BMI of 18.5 to 25.0?kg/m2; overweight was defined as a BMI of 25 to 30?kg/m2, and obese was defined as a BMI greater than 30?kg/m2. Subjects were classified as having type?2 diabetes if they met any 1 of the standard criteria for the disease.
Of the total study sample, 29 participants were normal weight, 51 were overweight, and 14 were obese.
Aging Effect
Multiple regression analyses revealed that BMI was negatively correlated with brain atrophy, and that type?2 diabetes and fasting plasma insulin levels were not. Specifically, the investigators found that a higher level of body tissue was associated with brain-tissue loss in the frontal and temporal lobes, the anterior cingulate gyrus, the hippocampus, and the basal ganglia.
Overweight individuals had brain loss in the basal ganglia, the corona radiate, and the parietal lobe. The authors report that negative correlations between body-tissue fat and brain structure were strongest in obese people, but were also seen in overweight people.
"The brains of obese people looked 16 years older than the brains of those who were lean, and in overweight people they looked 8 years older," said Dr. Thompson.
"It seems that, along with increased risk for health problems such as such type?2 diabetes and heart disease, obesity is bad for your brain. We have linked it to the shrinkage of brain areas that are targeted by Alzheimer's disease," study investigator Cyrus A. Raji, MD, from the University of Pittsburgh School of Medicine in Pennsylvania, said in a statement. "But that could mean that exercising, eating right, and keeping weight under control can maintain brain health with aging and potentially lower the risk for Alzheimer's and other dementias."
The researchers have disclosed no relevant financial relationships.
Hum Brain Mapp. Published online before print August 6, 2009. |
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