cbnmasd

作者：Nancy Fowler Larson  
出處：WebMD醫學新聞

　　January 19, 2010 — 根據發表於1月外科醫學誌(Archives of Surgery)的電腦模式基礎研究，進行最普遍的減重手術、胃繞道手術之後，病態肥胖的美國人可以多活3年。
　　
　　俄亥俄州辛辛納提大學、學院健康中心的Daniel P. Schauer醫師等人寫道，雖然沒有大型隨機控制試驗比較病態肥胖的減重手術和密集醫療處置，大型控制試驗和許多案例研究的證據顯示，對於身體質量指數(BMI)(計算方法是體重(kg)除以身高(m)的平方；kg/m2)40以上的成人，減重手術是目前唯一可以促進有臨床意義的減重、且改善肥胖相關情況的治療方法。許多回溯世代研究與1個前瞻研究認為，減重手術也可改善存活。
　　
　　該研究試圖衡量胃繞道手術對於病態肥胖的利益與風險，病態肥胖約佔美國人口的5.1%。
　　
　　研究者以多元邏輯回歸建立「馬可夫狀態轉移決策分析模式(Markov state transition decision analytic model)」，分析最常使用的胃繞道手術(美國病態肥胖者有65%以上接受此一手術)、未接受手術者之差異。研究者選擇一個42歲女性和44歲男性(兩人的BMI都達45 kg/m2)作為基礎案例分析。
　　
　　為了確認住院死亡率風險，作者們使用「2005年全國住院病患訪視調查」的23,281個案例，之後校正獲得30天死亡率的資料，在每個這類週期中，使用病患的BMI、手術狀態、年紀與性別計算他們的死亡風險。
　　
　　作者們使用1991至1996年的全國健康訪視調查、超過399,000名研究對象的資料，計算肥胖與超出的死亡風險的關聯。減重手術對於死亡率的效果被假設只有和與肥胖有關的過多死亡有關聯。關於該手術效果的資訊來自最近有研究價值的觀察試驗。
　　
　　【較年經、BMI較高的研究對象有最佳結果】
　　最後的多變項邏輯回歸模式使用7個因素— BMI、BMI2、年紀、年紀2、性別、性別× BMI、以及年紀× 性別— 來預測死亡率，資料模式適配度良好(Hosmer-Lemeshow模式適配度，P > .05；C 統計值，0.83)。
　　
　　電腦模式顯示，42歲女性的模式在手術後多活2.95年(35.03 vs 32.08 年)，當30天手術死亡率增加到超過9.5% (開始時的30天死亡率為0.2%)、或手術效果減少到2%以下時(開始時的效果為53%)，不傾向進行手術。
　　
　　根據該模式，44歲男性模式在手術後多活2.57年(26.82 vs 24.25年)。當30天手術死亡率增加到超過8.6%(開始時的30天死亡率為0.55%)、手術效果減少到3%以下時(開始時的效果為53%)，不傾向進行手術。
　　
　　在兩性中，較年輕者以及BMI較高者，生活餘命增加最多，在男性中，各年齡層與各類別的增加略(比女性)少。
　　
　　作者們寫道，個別病患的適當決策根據手術前後死亡率、隨著BMI增加而升高的年度死亡率、以及手術效果之間的利益與風險而有不同；不過，對於一般的病態肥胖病患，胃繞道手術增加了生活餘命。
　　
　　【多種研究限制】
　　作者們指出以下的研究限制：
　　* 現有的資料不包括BMI與其他臨床變項
　　* 所有計算手術效果的資料來自單一州(猶他州)
　　* 作者們的模式中並未納入長期的、術後併發症、或任何必要的修訂。
　　* 生活餘命是唯一測量的結果，沒有縱向研究探討生活品質的改善。
　　
　　研究作者結論表示，並非所有的胃繞道手術都有好結果，他們有關生活餘命較長的發現，將有助醫師確認哪些病患是最好的手術對象。
　　
　　作者們寫道，我們相信，這個分析結果可以更有助於病患和醫師有關胃繞道手術的決定。
　　
　　國家糖尿病與消化道和腎臟疾病研究中心支持本研究，研究作者們皆宣告沒有相關財務關係。  


Gastric Bypass Surgery May Prolong Lives of Morbidly Obese

By Nancy Fowler Larson
Medscape Medical News

January 19, 2010 — Morbidly obese Americans could live up to 3 years longer after undergoing gastric bypass surgery, the most popular bariatric surgical procedure, according to a computerized model-based study published in the January issue of the Archives of Surgery.

"While no large-scale randomized controlled trials have compared bariatric surgery with intensive medical management for the morbidly obese, there is evidence from large controlled trials and numerous case series that bariatric surgery is currently the only effective therapy for promoting clinically significant weight loss and improving obesity-associated conditions among adults with a body mass index (BMI) of 40 or higher (calculated as weight in kilograms divided by height in meters squared)," write Daniel P. Schauer, MD, MSc, from the University of Cincinnati Academic Health Center, Ohio, and colleagues. "Several retrospective cohort studies and 1 prospective study suggest that bariatric surgery also improves survival."

The study sought to weigh the benefits of gastric bypass surgery against its risks in the morbidly obese, who make up 5.1% of the US population.

The researchers created a decision analytic Markov state transition model with multiple logistic regression as inputs to analyze the differences between having gastric bypass, the leading surgery (>65% of all patients who receive bariatric surgery) for the morbidly obese in the United States, vs undergoing no surgery. A 42-year-old woman and 44-year-old man, both with BMIs of 45 kg/m2, were chosen for the researchers' base case analysis.

To determine in-hospital mortality risk, the authors used 23,281 cases from the 2005 National Inpatient Interview Survey and then adjusted the data for 30-day mortality. During each such cycle, patients' risk for death was calculated using their BMI, surgical status, age, and sex.

Data from more than 399,000 participants from the 1991 to 1996 National Health Interview Survey were used to calculate excess mortality's relationship with obesity. Bariatric surgery's effect on mortality was assumed only in connection with excess deaths associated with obesity. Information about the surgery's effectiveness was gathered from a recently conducted, substantial observational trial.

Younger, Higher-BMI Participants Had Best Results

The ultimate multivariable logistic regression model used 7 factors — BMI, BMI2, age, age2, sex, sex × BMI, and age × sex — to predict mortality, with a good fit to the data (Hosmer-Lemeshow goodness-of-fit, P > .05; c statistic, 0.83).

The computerized model showed that the 42-year-old female model lived 2.95 years longer (35.03 vs 32.08 years) after undergoing surgery. When 30-day surgical mortality increased to more than 9.5% (baseline 30-day mortality, 0.2%) or when surgical efficacy declined to 2% or less (baseline efficacy, 53%), surgery was not preferred.

The 44-year-old male model would live 2.57 years longer (26.82 vs 24.25 years) after undergoing surgery, according to the model. Surgical treatment was not preferred when 30-day surgical mortality rose above 8.6% (baseline 30-day mortality, 0.55%) or when the effectiveness of the surgery fell to 3% or less (baseline efficacy, 53%).

In both sexes, those who were younger and had a higher BMI had the largest life expectancy increases. In men, the increase was slightly lower for all ages and subgroups.

"The optimal decision for individual patients varies depending on the balance of risks between perioperative mortality, excess annual mortality associated with increasing BMI, and the efficacy of surgery; however, for the average morbidly obese patient, gastric bypass surgery increases life expectancy," the authors write.

Multiple Study Limitations

The authors noted several limitations to their assessments:

Available data do not include BMI and other clinical variables.
All data for calculating surgery efficacy are from a single state (Utah).
The authors did not model long-term, postsurgical complications, including any necessary revision.
Life expectancy was the sole outcome metric, as there are no longitudinal studies exploring quality-of-life improvements.
Acknowledging that not all gastric bypass surgeries produce good results, the study authors concluded that their findings of longer life spans for most subjects will help physicians determine which patients are the best candidates.

"We believe results of this analysis can be used to better inform both patients' and physicians' decisions regarding gastric bypass surgery," the authors write.

The National Institute of Diabetes and Digestive and Kidney Diseases supported the study. The study authors have disclosed no relevant financial relationships.

Arch Surg. 2010;145:57-62.