運動降低大腸息肉風險及大腸癌發生率


  【24drs.com】一項線上發表在英國癌症期刊的研究結果指出,我們可能藉由運動降低癌前息肉的風險,進而減少大腸癌的發生率。
  
  密蘇里聖路易斯華盛頓大學醫學公共衛生服務部門的Kathleen Wolin醫師指出,我們知道活躍的生活型態可以保護免於罹患大腸癌,但是這項研究是第一項檢閱目前可獲得的證據且證實大腸息肉的減少是最可能的解釋。
  
  該團隊的早期研究、以及其他研究已經證實運動可以減少大腸癌風險達25%。
  
  這項新研究是根據20項研究的綜合分析,針對大腸腺瘤─在乙狀結腸鏡或大腸鏡檢時移除的癌前息肉進行研究。研究人員發現,常規運動與大腸息肉發生風險降低16%有關,且降低較大或較後期的息肉風險達30%,這些息肉比較可能癌化。
  
  Wolin醫師在一項聲明中表示,運動有許多好處,包括強化免疫系統,減少大腸發炎,並協助降低胰島素濃度,我們都知道這些因素可能影響大腸息肉風險。
  
  英國癌症研究健康資訊主任Sara Hion在同一份聲明中指出,這項研究加強了規律運動可以顯著降低大腸癌風險的證據強度,這是一份友情推廣該研究的聲明。她附帶表示,我們建議每天至少從事半小時的運動。
  
  美國癌症醫學會(ACS)也建議每週至少五天從事30分鐘以上的運動,而45至60分鐘的活動是更好的。根據最近一篇ACS報告(大腸直腸癌數據與圖表2011-2013),運動對大腸癌風險的保護作用是所有報導中最為一致的。
  
  【新研究結果】
  為了這項新研究,Wolin醫師與同事們分析20項臨床試驗收集而來的數據,這些研究報告接受乙狀結腸鏡或大腸鏡(有症狀與接受篩檢)患者的運動程度(主要從問卷取得)。大部分研究並沒有指出接受這些檢查的原因。
  
  整體來說,運動量與大腸息肉(固定模式相對風險[RR]為0.87;95%信賴區間[CI]為0.83-0.91;隨機分派模式RR為0.84;95% CI為0.77-0.92)有顯著反向關係。研究中,風險下降不分男女性。
  
  研究人員表示,運動量的效應有侷限於較大或後期腺瘤的趨勢,而非低度的那些腫瘤。他們附帶表示,這項綜合分析發現對較大的或較後期的腺瘤,效應比整體強烈,雖然並未達顯著水準。
  
  他們報告,當分析限制在18項腺瘤息肉與其他息肉(例如增生的、惡性的息肉)分開的研究時,這樣的風險下降(RR為0.83)大部分並未改變。
  
  【牽涉到整個癌化過程】
  Wolin醫師與同事們表示,部分較早期的報告未能證實運動量與大腸息肉之間的關係;這可以闡釋為身體活性對腺瘤轉換成大腸息肉之間的過程,比起腺瘤發生更為重要。
  
  然而,他們報告這項整合性綜合分析與許多過去的研究報告顯示運動可以降低大腸癌風險,代表運動量可能在整個癌化過程中扮演角色。
  
  Wolin醫師與同事們表示,許多機轉被認為與這些效應有關,包括加強免疫功能、降低發炎反應、降低胰島素濃度與胰島素抵抗性,以及提升維生素D濃度。
  
  研究人員表示沒有相關資金上的往來。其中一位作者,來自華盛頓大學醫學院的G.A. Colditz醫師接受美國癌症學會臨床研究教授資金贊助。
  
  資料來源:http://www.24drs.com/professional/list/content.asp?x_idno=6476&x_classno=0&x_chkdelpoint=Y
  

Exercise Reduces Risk for Colon Polyps, Resulting in Less Colon Cancer

By Zosia Chustecka
Medscape Medical News

March 9, 2011 — Exercise might reduce the risk for colon cancer by reducing the risk of developing precancerous polyps, according to a new study published online March 2 in the British Journal of Cancer.

"We've long known that an active lifestyle can protect against bowel cancer, but this study is the first to look at all the available evidence and to show that a reduction in bowel polyps is the most likely explanation for this," said lead author Kathleen Wolin, MD, from the division of public health services at the Washington University School of Medicine in St. Louis, Missouri.

Earlier work by the same group, as well as other research, has shown that exercise can reduce the risk for colon cancer by 25%.

This new study, based on a meta-analysis of 20 studies, focused on colon adenomas, the precancerous polyps that are removed during sigmoidoscopy or colonoscopy. The researchers found that regular physical exercise was associated with a 16% decrease in the risk of developing colon polyps, and with a 30% decrease in the risk of developing polyps that were large or advanced, and thus more likely to become cancerous.

"Exercise has many benefits, including boosting the immune system, decreasing inflammation in the bowel, and helping to reduce insulin levels — all factors that we know are likely to have an effect on bowel polyp risk," Dr. Wolin said in a statement.

"This study adds weight to the evidence showing that regular exercise can substantially cut the risk of bowel cancer," said Sara Hiom, director of health information at Cancer Research UK, in the same statement, which was issued by the charity to publicize the study. "We recommend doing at least half an hour's moderate exercise a day," she added.

The American Cancer Society (ACS) also recommends at least 30 minutes of at least moderate activity on 5 days or more per week, and says that 45 to 60 minutes of intentional physical activity is preferable. The protective effect of exercise on colon cancer risk is "one of the most consistently reported relationships," according to a recent ACS report, Colorectal Cancer Facts & Figures 2011-2013.

New Study

For the new study, Dr. Wolin and colleagues reanalyzed data collected in 20 clinical trials that reported on physical activity levels (obtained mainly from questionnaires) in individuals who had undergone sigmoidoscopy or colonoscopy (both symptomatic and screening). Most studies did not specify the reason for undergoing the procedure.

Together, these trials involved more than 250,000 individuals.

Overall, there was a significant inverse association between physical activity and colon polyps (fixed-effect relative risk [RR], 0.87; 95% confidence interval [CI], 0.83 to 0.91; random-effects RR, 0.84; 95% CI, 0.77 to 0.92).

The risk reduction was similar in men and women.

"There was a tendency for the effect of physical activity to be restricted to large or advanced adenomas, and not low-grade ones," the researchers note.

"Our meta-analysis found the effect was stronger, though not significantly so, for large or advanced adenomas than for the overall effect," they add.

The risk reduction (RR, 0.83) was "largely unchanged" when the analysis was restricted to the 18 studies in which the results for adenomatous polyps were separated from all polyps (i.e., hyperplastic, malignant polyps), they report.

Involved in Whole Carcinogenic Process

Dr. Wolin and colleagues note that some earlier reports failed to show an association between physical activity and colon polyps; this has been interpreted as suggesting that physical activity might be more important in the "adenoma to carcinoma" sequence than in adenoma development.

However, they report that this comprehensive meta-analysis — together with numerous previous reports demonstrating that physical activity can reduce the risk for colon cancer — suggests that physical activity plays a role across the whole carcinogenic process.

Several mechanisms have been proposed for such effects, including enhanced immune function, decreased inflammation, reduced insulin levels and insulin resistance, and higher vitamin D levels, Dr. Wolin and colleagues note.

The researchers have disclosed no relevant financial relationships. One of the coauthors, G.A. Colditz, MD, DrPH, from the Washington University School of Medicine, was supported by an American Cancer Society Clinical Research Professorship.

Br J Cancer. 2011;104:882-885.

    
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