高強度有氧運動改善MCI病患、特別是女性的認知表現


  【24drs.com】January 21, 2010 — 一篇新研究認為,高強度、受監督的有氧運動計畫可改善輕微認知缺損(mild cognitive impairment,MCI)成人的認知表現,而且女性的效果特別明顯,但是兩性在心肺適能的增加與體脂肪降低方面效果相當。
  
  這些結果登載於1月號的神經醫學誌(Archives of Neurology),研究顯示6個月的有氧運動計畫改善了MCI婦女的多項執行功能檢測表現,此一運動計畫也改善了女性的胰島素敏感性與降低壓力荷爾蒙,而男性的效果較小。
  
  華盛頓大學醫學院的Laura Baker博士向Medscape Neurology表示,我們通常知道年紀或疾病、我們利用葡萄糖的效率較少,之後發現認知問題,因此,如果我們可以增加葡萄糖代謝效率,或許可以改善葡萄糖進入腦部的效率,因而改善認知,女性有此效果,男性則無。
  
  【有氧運動與伸展操】
  為了進行該研究,有33名失憶型MCI成人、其中17名女性,被隨機分派接受高強度有氧運動計畫或者伸展操(對照組)。研究者指出,有氧運動組在一個體適能訓練員監督下運動,每天45-60分鐘、儲備心跳率75%- 85%,每週4天為期6個月。
  
  對照組遵守同樣的運動時間表,但是是在監督下進行伸展操,心律維持在儲備心跳率50%以下。所有研究者在研究前後進行葡萄糖代謝檢測與踩腳踏車測驗,在開始時與第3和第6個月時抽血和進行認知測驗。
  
  最初的8堂課由訓練員監督,之後,每位研究對象每週只有被訓練員監督1堂課,研究者報告指出,6個月的有氧運動與伸展操,比較心肺適能的改善,指標是利用踩腳踏車測量VO2尖峰值、以及腳踏車設定等級和精疲力竭的時間。
  
  這套有氧運動處方也改善了多重任務的執行控制過程、認知彈性、資訊處理效率、以及選擇性注意力。他們寫道,當把性別納入作為模式的測變項時,一個明顯的交互作用指出,男女之間對這種治療有不同的效果,對於女性,增加VO2尖峰值與改善執行功能有關聯。
  
  有氧運動對於符號數字形式測驗和語言流暢度檢測等認知功能測量也有不錯的效果,分析再度發現,這兩種檢測的效果在女性都大於男性,叫色測驗(Stroop test)也有類似的性別差異,有氧運動對男性沒有效果。相較於伸展操組,有氧運度動組比開始時更快完成軌跡B測試(Trails B test); 這項效果在男女性之間相似。
  
  研究作者們指出,有氧運動在葡萄糖調節和胰島素敏感性方面也有性別相關的改善,對於女性,胰島素敏感性在6個月時的改變可預測VO2尖峰值和執行功能。
  
  血漿可體松值方面,也發現有氧運動有性別特定效果,伸展操組的女性增加,有氧運動組女性則無,至於男性,伸展操組的可體松值降低,有氧運動組的男性保持穩定。
  
  有氧運動也降低了女性的腦衍生神經滋養因子(brain-derived neurotrophic factor,BDNF),男性則無。
  
  【行動和組織】
  如同Baker博士所觀察的, MCI病患最初受到影響的認知能力是行動和組織力,一般而言,這是像清掃和完成一些計畫等小事,運動和任何其他工作並無不同,MCI病患會擔心運動,他們沒有信心正確運動。
  
  她指出,因此,這些人需要幫助才會去「滾球」。不過,一旦建立一個結構,且他們開始從事該運動處方,他們狀況都很好,實際上,最初6週的運動處方讓病患慢慢達到目標心律,我們相當鼓勵他們運動,之後,到第6週時,很多人已經達到他們的目標心律。
  
  Baker博士觀察指出,證據顯示,運動對於正常、沒有特殊記憶問題的年長成人有幫助,我們希望,延長運動可以延緩認知缺損之MCI病患的認知衰退,因為我們無法逆轉認知衰退,如果我們可以讓人有幾個月比較好的生活品質,將會是很大的成就。
  
  梅約診所的Yonas Geda醫師等人在這期神經醫學誌發表的另一篇研究指出,中老年時適度運動可降低正常認知功能成人的MCI風險達39%。
  
  這項研究的結果發現男性和女性有一致的結果。
  
  【重要的缺口】
  伊利諾大學Urbana-Champaign分校的Art Kramer博士向Medscape Neurology表示,該研究開始填補一個更佳瞭解運動對MCI病患之影響的重要缺口,有許多關於健康年長者的運動研究,但是很少對MCI或阿茲海默氏症研究,嚴謹的控制試驗是重要的。
  
  Kramer博士等人在對於體適能和認知的統合分析(Psychol Sci. 2003;14:125-130)中,也發現體適能對於認知有正面影響。
  
  他指出,許多研究有一致的見解,運動對於女性的效果大於男性,另一方面,目前的研究雖然控制良好,仍然只有少數樣本,男性缺乏有氧運動的效果或許是因為研究樣本有限所致。
  
  Kramer博士觀察指出,如同作者們所認為的,這是初步資料,需要以較大型的MCI病患隨機控制試驗來重現,或許可進一步加入阿茲海默氏症病患,不過,他指出,該研究試圖在動物研究中找出運動對可體松和BDNF的效果,進行許多生理和神經檢測,這是很好的一步。
  
  退伍軍人事務部以及阿茲海默氏症協會支持該研究。作者們皆宣告沒有相關財務關係。Kramer博士宣告沒有相關資金上的往來。

High-Intensity Aerobics Improves Cognitive Performance in MCI, Especially for Women

By Emma Hitt, PhD
Medscape Medical News

January 21, 2010 — A high-intensity, supervised aerobic exercise program improves cognitive performance in older adults with mild cognitive impairment (MCI), a new study suggests. The effects are most pronounced in women despite comparable gains in cardiorespiratory fitness and body fat reduction in both sexes.

The results, published in the January issue of the Archives of Neurology, showed that a 6-month aerobic exercise program improved performance on multiple tests of executive function in women with MCI. The same exercise regimen also improved insulin sensitivity and reduced stress hormones in women but had much less effect in men.

"What we know is that generally with age or disease, we use glucose less efficiently and then we see cognitive problems," Laura Baker, PhD, University of Washington School of Medicine, Seattle, told Medscape Neurology. "So if we can increase the efficacy of glucose metabolism, we may be improving the efficacy with which glucose gets to the brain and therefore improve cognition. This happened for women but not for men."

Aerobics vs Stretching

For the study, 33 adults, of whom 17 were women, with amnestic MCI were randomized to either a high-intensity aerobic exercise program or a stretching control group. "The aerobic group exercised under the supervision of a fitness trainer at 75% to 85% of heart rate reserve for 45 to 60 minutes per day, 4 days per week for 6 months," the investigators note.

The control group followed the same schedule during which they performed supervised stretching activities but maintained their heart rate at or below 50% of their heart rate reserve. Glucometabolic and treadmill tests were done before and after the study on all participants, and blood was collected and the cognitive test administered at baseline and again at months 3 and 6.

The first 8 sessions were supervised by the trainer, and thereafter, the trainer supervised 1 session per week per participant. "Six months of controlled aerobic exercise vs stretching improved cardiorespiratory fitness indexed by exercise treadmill test measures of VO2 peak ... treadmill grade ... and treadmill time to exhaustion," the investigators report.

The same aerobic regimen also improved executive control processes of multitasking, cognitive flexibility, information processing efficiency, and selective attention. When sex was included in the model as a predictor variable, they write, "a significant interaction indicated that this treatment effect differed for men and women, [whereas] for women, increasing VO2 peak was associated with improved executive function."

Favorable effects of aerobic exercise were also apparent for Symbol-Digit Modalities and Verbal Fluency, measures of cognitive function, with analyses again revealing that the effect size was larger for women than for men on both tasks. Sex differences were also observed on the Stroop test, with aerobic exercise having no effect in men. The aerobic group was also faster to complete the Trails B test compared with baseline than the stretching control group; here, the effect was similar for women and men.

"Aerobic exercise was [also] associated with sex-specific improvements in glucoregulation and insulin sensitivity," the study authors note, "and for women, 6-month changes in insulin sensitivity predicted VO2 peak and executive function."

A sex-specific effect of aerobic exercise was again observed for plasma cortisol levels, increasing for women in the stretching control group over the study interval but not for women in the aerobic group. In men, cortisol levels decreased over time for those in the stretching group, whereas they remained stable for the aerobic group.

Aerobic exercise also reduced brain-derived neurotrophic factor (BDNF) in women but not in men.

Initiate and Organize

As Dr. Baker observes, the first cognitive ability to be affected in patients with MCI is their ability to initiate and to organize. "Generally, it's the little things like cleaning up or finishing off projects, and exercise is no different than any other task." Patients with MCI are also afraid to exercise, and they have no confidence that if they exercise they might do it right.

Thus, these people need help to "get the ball rolling," she adds. Once a structure is in place, however, and they get started on an exercise regimen, "they are really fine." Indeed, after the first 6 weeks of their exercise regimen during which patients were worked up to their target heart rate very slowly, "we were exercising them at a pretty high level, and by week 6, many of them were going over their target [heart rate]," Dr. Baker notes.

"Evidence already shows that there is a benefit from exercise for normal older adults with no specific memory problems, and our hope is that prolonged exercise may slow progression in cognitive decline in patients with MCI because even if we can't reverse cognitive decline altogether, if we can give someone a better quality of life for many months, that would be a huge accomplishment," Dr. Baker observes.

In a related but separate study published in the same issue of Archives of Neurology by Yonas Geda, MD, and colleagues at the Mayo Clinic in Rochester, Minnesota, moderate exercise done during mid or even later in life reduced the risk of MCI by 39% in adults with normal cognitive function at baseline.

Findings in this study were consistent among both men and women.

Important Gap

Art Kramer, PhD, University of Illinois at Urbana-Champaign, told Medscape Neurology that the study begins to fill an important gap toward a better understanding of the potential impact exercise may have in MCI patients. "There are many exercise studies with relatively healthy older individuals but very few with MCI or Alzheimer's disease, and rigorously controlled trials are important."

In their own meta-analysis of fitness and cognition (Psychol Sci. 2003;14:125-130), Dr. Kramer and colleagues also found that fitness positively affects cognition.

"Consistent across the many studies, the effect of exercise was larger for women than it is for men," he adds. On the other hand, the current study, although well controlled, still involves only a small sample and perhaps the lack of effect from aerobic exercise in men may be explained by the limited numbers of patients in the study overall.

"As the authors themselves suggest, this is preliminary data and it needs to be replicated ideally in a larger randomized controlled trial of MCI patients and perhaps even those further along with Alzheimer's disease," Dr. Kramer observes. Still, he adds, "the study attempts to relate the effects of exercise on cortisol and BDNF to animal work in which we have more physiological and neurological measures, which is a good step."

The study was supported by the Department of Veterans Affairs and the Alzheimer’s Association. The authors have disclosed no relevant financial relationships. Dr. Kramer has disclosed no relevant financial relationships.

Arch Neurol. 2010;67:71-79, 80-86.

    
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