J. C. Zhang, Department of Medicine, University of Toronto, Toronto, Ontario, Canada J. Matelski, Biostatistics Research Unit, University Health Network, University of Toronto, Toronto, Ontario, Canada R. Gandhi, Division of Orthopaedic Surgery and Krembil Research Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada T. Jackson, Department of Surgery, University Heath Network, University of Toronto, Toronto, Ontario, Canada R. Gandhi, T. Jackson, D. Urbach, Department of Surgery, University of Toronto, Toronto, Ontario, Canada D. Urbach, Department of Surgery, Women's College Hospital, University of Toronto, Toronto, Ontario, Canada P. Cram, Division of General Internal Medicine, Sinai Health System and University Health Network, Toronto, Ontario, Canada.
Clin Orthop Relat Res. 2018 May;476(5):964-973. doi: 10.1007/s11999.0000000000000218.
The "obesity paradox" is a phenomenon described in prior research in which patients who are obese have been shown to have lower postoperative mortality and morbidity compared with normal-weight individuals. The paradox is that clinical experience suggests that obesity is a risk factor for difficult wound healing and adverse cardiovascular outcomes. We suspect that the obesity paradox may reflect selection bias in which only the healthiest patients who are obese are offered surgery, whereas nonobese surgical patients are comprised of both healthy and unhealthy individuals. We questioned whether the obesity paradox (decreased mortality for patients who are obese) would be present in nonurgent hip surgery in which patients can be carefully selected for surgery but absent in urgent hip surgery where patient selection is minimized.
QUESTIONS/PURPOSES: (1) What is the association between obesity and postoperative mortality in urgent and nonurgent hip surgery? (2) How is obesity associated with individual postoperative complications in urgent and nonurgent hip surgery? (3) How is underweight status associated with postoperative mortality and complications in urgent and nonurgent hip surgery?
We used 2011 to 2014 data from the American College of Surgeons National Surgical Quality Improvement Project (ACS-NSQIP) to identify all adults who underwent nonurgent hip surgery (n = 63,148) and urgent hip surgery (n = 29,047). We used logistic regression models, controlling for covariants including age, sex, anesthesia risk, and comorbidities, to examine the relationship between body mass _index (BMI) category (classified as underweight < 18.5 kg/m, normal 18.5-24.9 kg/m, overweight 25-29.9 kg/m, obese 30-39.9 kg/m, and morbidly obese > 40 kg/m) and adverse outcomes including 30-day mortality and surgical complications including wound complications and cardiovascular events.
For patients undergoing nonurgent hip surgery, regression models demonstrate that patients who are morbidly obese were less likely to die within 30 days after surgery (odds ratio [OR], 0.12; 95% confidence interval [CI], 0.01-0.57; p = 0.038) compared with patients with normal BMI, consistent with the obesity paradox. For patients undergoing urgent hip surgery, patients who are morbidly obese had similar odds of death within 30 days compared with patients with normal BMI (OR, 1.18; 95% CI, 0.76-1.76; p = 0.54). Patients who are morbidly obese had higher odds of wound complications in both nonurgent (OR, 4.93; 95% CI, 3.68-6.65; p < 0.001) and urgent cohorts (OR, 4.85; 95% CI, 3.27-7.01; p < 0.001) compared with normal-weight patients. Underweight patients were more likely to die within 30 days in both nonurgent (OR, 3.79; 95% CI, 1.10-9.97; p = 0.015) and urgent cohorts (OR, 1.47; 95% CI, 1.23-1.75; p < 0.001) compared with normal-weight patients.
Patients who are morbidly obese appear to have a reduced risk of death in 30 days after nonurgent hip surgery, but not for urgent hip surgery. Our results suggest that the obesity paradox may be an artifact of selection bias introduced by careful selection of the healthiest patients who are obese for elective hip surgery. Surgeons should continue to consider obesity a risk factor for postoperative mortality and complications such as wound infections for both urgent and nonurgent surgery.
Level III, therapeutic study.
“肥胖悖论”是先前研究中描述的一种现象，即与正常体重的个体相比，肥胖患者的术后死亡率和发病率较低。悖论是，临床经验表明肥胖是伤口愈合困难和不良心血管结局的危险因素。我们怀疑肥胖悖论可能反映了选择偏差，即只有身体最健康的肥胖患者才被提供手术，而接受非肥胖手术的患者则既有健康的也有不健康的个体。我们想知道肥胖悖论（肥胖患者的死亡率降低）是否会出现在非紧急髋关节手术中，因为在这种手术中可以仔细选择患者进行手术，但在紧急髋关节手术中，患者选择最小化。
问题/目的：（1）肥胖与紧急和非紧急髋关节手术的术后死亡率有何关联？（2）肥胖与紧急和非紧急髋关节手术中的个体术后并发症有何关联？（3）体重过轻与紧急和非紧急髋关节手术中的术后死亡率和并发症有何关联？
我们使用了美国外科医师学院国家手术质量改进计划（ACS-NSQIP）2011 年至 2014 年的数据，确定了所有接受非紧急髋关节手术（n=63148）和紧急髋关节手术（n=29047）的成年人。我们使用逻辑回归模型，控制了年龄、性别、麻醉风险和合并症等协变量，以检查体重指数（BMI）类别（分类为体重过轻<18.5kg/m2、正常 18.5-24.9kg/m2、超重 25-29.9kg/m2、肥胖 30-39.9kg/m2 和病态肥胖>40kg/m2）与不良结果（包括 30 天死亡率和手术并发症，包括伤口并发症和心血管事件）之间的关系。
对于接受非紧急髋关节手术的患者，回归模型显示病态肥胖患者在手术后 30 天内死亡的可能性较小（比值比[OR]，0.12；95%置信区间[CI]，0.01-0.57；p=0.038），与肥胖悖论一致。对于接受紧急髋关节手术的患者，病态肥胖患者与正常 BMI 患者相比，在 30 天内死亡的可能性相似（OR，1.18；95%CI，0.76-1.76；p=0.54）。病态肥胖患者在非紧急（OR，4.93；95%CI，3.68-6.65；p<0.001）和紧急队列（OR，4.85；95%CI，3.27-7.01；p<0.001）中发生伤口并发症的可能性更高。体重过轻的患者在非紧急（OR，3.79；95%CI，1.10-9.97；p=0.015）和紧急队列（OR，1.47；95%CI，1.23-1.75；p<0.001）中在 30 天内死亡的可能性更高。
病态肥胖患者在非紧急髋关节手术后 30 天内死亡的风险似乎降低，但紧急髋关节手术则不然。我们的结果表明，肥胖悖论可能是由于对择期髋关节手术的最健康肥胖患者进行了精心选择而引入的选择偏差的一种表现。外科医生应该继续认为肥胖是术后死亡率和并发症（如伤口感染）的危险因素，无论是紧急手术还是非紧急手术。
三级，治疗性研究。
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