The influence of body mass index obesity status on vascular surgery 30-day morbidity and mortality.
OBJECTIVE
Mild obesity may have a protective effect against some diseases, termed an "obesity paradox." This study examined the effect of body mass index (Kg/m(2) BMI) on surgical 30-day morbidity and mortality in patients undergoing vascular surgical procedures.


METHODS
As part of the National Surgical Quality Improvement Program (NSQIP), demographic and clinical risk variables, mortality, and 22 defined complications (morbidity) were obtained over three years from vascular services at 14 medical centers. At each medical center, patients from the operative schedule were prospectively and systematically enrolled according to NSQIP protocols. Outcomes and risk variables were compared across NIH-defined obesity classes (underweight [BMI<or=18.5], normal [18.5<BMI<25], overweight [25<BMI<or=30], obese I [30<BMI<or=35], obese II [35<BMI<or=40], and obese III [BMI>40]) using analysis of variance and means comparisons. Logistic regression was used to control for other risk factors.


RESULTS
Vascular procedures in 7,543 patients included lower extremity revascularization (24.6%), aneurysm repair (17.4%), cerebrovascular procedures (17.3%), amputations (9.4%), and "other" procedures (31.3%). In the entire cohort, there were 1,659 (22.0%) patients with complications and 295 (3.9%) deaths. Risk factors of hypertension and diabetes increased with BMI (analysis of variance [ANOVA] P < .05) as expected; smoking, disseminated cancer, and stroke decreased (ANOVA P < .01). Twenty other risk factors, as well as mortality and morbidity, had "U" or "J"-shaped distributions with the highest incidence in underweight and/or obese class III extremes but reduced minimums in overweight or obese I classes (ANOVA P < .05). After controlling for age, gender, and operation type, mortality risk remained lowest in obese class I patients (Odds ratio [OR] 0.63, P = .023) while morbidity risk was highest in obese class III patients (OR 1.70, P = .0003), due to wound infection, thromboembolism, and renal complications.


CONCLUSIONS
Underweight patients have poorer outcomes and class III obesity is associated with increased morbidity. Mildly obese patients have reduced co-morbid illness, surprisingly even less than normal-class patients, with correspondingly reduced mortality. Mild obesity is not a risk factor for 30-day outcomes after vascular surgery and confers an advantage.
Davenport
Daniel L
DL
Department of Surgery, University of Kentucky, Lexington, KY 40536-0298, USA. Daniel.Davenport@uky.edu
Xenos
Eleftherios S
ES
Hosokawa
Patrick
P
Radford
Jacob
J
Henderson
William G
WG
Endean
Eric D
ED
D000328:Adult; D000368:Aged; D015992:Body Mass Index; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications* / Q000401:mortality; D011446:Prospective Studies; D011787:Quality of Health Care; D018570:Risk Assessment; D012307:Risk Factors; D012720:Severity of Illness Index; D013851:Thinness / Q000150:complications* / Q000401:mortality; D013997:Time Factors; D016896:Treatment Outcome; D014481:United States; D014652:Vascular Diseases / Q000150:complications / Q000401:mortality / Q000601:surgery*; D014656:Vascular Surgical Procedures / Q000009:adverse effects / Q000401:mortality / Q000592:standards