Class I obesity is paradoxically associated with decreased risk of postoperative stroke after carotid endarterectomy

Abstract

Although obesity is a risk factor for vascular disease, previous studies have shown an obesity paradox with decreased mortality in obese patients undergoing vascular surgery. This study examined the relationship between body mass index (BMI) and outcomes after carotid endarterectomy (CEA). The 2005-2009 American College of Surgeons National Surgical Quality Improvement Program database was queried to evaluate 30-day outcomes after isolated CEA across National Institutes of Health-defined obesity classes. χ(2) analysis was used to assess the unadjusted relationship of BMI category to postoperative outcomes. The independent association of BMI with morbidity and mortality was assessed with multivariable logistic regression, adjusting for preoperative and operative characteristics. In the cohort of 23,652 CEA, 1.8% of patients were underweight (BMI <18.5), 26.6% were normal weight (BMI 18.5-24.9), 39.4% were overweight (BMI 25.0-29.9), 21.1% were class I obese (BMI 30.0-34.9), 7.5% were class II obese (BMI 35.0-39.9), and 3.5% were class III obese (BMI ≥ 40). The overall stroke and mortality rates were 1.4% and 0.6%, respectively. On univariable analysis, there were U-shaped relationships between death (P = .017) and stroke (P = .029), with the lowest incidence in overweight and class I obese patients. The incidence of surgical site infection (SSI) (P = .021) increased incrementally with increasing BMI. On multivariable analysis, class I obesity was the only variable associated with decreased risk of stroke (odds ratio [OR], 0.51; 95% confidence interval [CI], 0.31-0.83; P = .007). Independent risk factors for stroke were previous transient ischemic attack (OR, 1.97; P = .006), American Society of Anesthesiologists class 4 to 5 (OR, 1.62; P = .010), surgery performed by a nonvascular surgeon (OR, 1.85; P = .015), and hemiplegia (OR, 1.97; P = .018). There was also a trend, although not statistically significant, toward decreased mortality risk associated with class I obesity (OR, 0.53; 95% CI, .26-1.08; P = .080). Class II obesity was associated with an increased risk of SSI compared with normal weight (OR, 2.21; 95% CI, 1.01-4.82; P = .047). BMI category was not associated with the risk of myocardial infarction. An obesity paradox exists for stroke and mortality after CEA; for stroke, but not mortality, this protective association was independent of patient demographics and comorbidities. Obesity is not a contraindication to CEA, and surgeons may safely undertake CEA in obese patients when indicated.