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Percent Body Fat as a Risk Factor for Surgical Complications
Yoon S. Chun, M.D.1, Christina Sun, B.A.2, Frank Lau, M.D.3, Heather Rosen, M.D., M.P.H.4, Elof Eriksson, M.D., Ph.D.1.
1Brigham and Women's Hospital, Boston, MA, USA, 2Harvard Medical School, Boston, MA, USA, 3Harvard Plastic Surgery Residency Program, Boston, MA, USA, 4Vanderbilt University Medical Center, Nashville, TN, USA.
PURPOSE: Obesity is a multifactorial disease affecting an increasing percentage of the United States population and is well-established risk factor for surgical complications. While body mass index (BMI) has traditionally been employed as a measure of obesity, it does not assess body composition, failing to distinguish adipose from other soft tissues. In contrast, percent body fat (%BF), measured by bioelectrical impedance analysis (BIA), can accurately reflect body adiposity and serves as a better indicator for obesity. This study was performed to evaluate obesity, as defined by %BF, as a risk factor for surgical complications.
METHODS: This prospective study included patients 18 to 64 years of age undergoing elective surgery at the Brigham and Women’s Faulkner Hospital since April 2012. Percent body fat was measured as part of routine preoperative assessment. Obesity was defined as %BF>31% in women and %BF>25% in men. All consecutive patients undergoing surgical procedures under general anesthesia were included. Exclusion criteria included neutropenia, immunosuppression, metastatic disease, or infection. Preoperative, operative, and 90-day postoperative data were collected through medical record review.
RESULTS: A total of 257 patients were included in the study and the data collection is currently ongoing. Among the study cohort, 181 (70.4%) patients were obese and 76 (29.6%) patients were non-obese by %BF, while 94 (36.6%) patients were obese and 163 (63.4%) patients were non-obese by BMI. Mean %BF and BMI were 34.1 ± 9.9% and 29.3 ± 6.6%, respectively. A total of 33 (12.8%) patients experienced postoperative complications. With obesity defined by %BF, postoperative complication rate was significantly higher in the obese group vs. the non-obese group (15.5% vs. 6.6%, p=0.05). With obesity defined by BMI, there was no significant difference in complication rate between the obese and non-obese group (13.8% vs. 12.3%; p=0.72). There was no significant difference in the demographic or clinical characteristics between obese group defined by %BF and those defined by BMI. Logistic regression analysis showed a cutpoint whereby patients with %BF>31% experienced a significantly higher complication rate than those patients below this threshold (OR=4.86; p=0.004).
CONCLUSION: Obesity, as measured by %BF, is significantly associated with increased surgical complication rate and may be a better indicator for obesity and predictor for postoperative complications than traditionally used BMI. An index value of 31% body fat is associated with an over four-fold higher risk of complications.
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