Defining a Safe Body Mass Index Threshold in Plastic Surgery: An NSQIP Analysis of BMI, Comorbidities, and...

Historically, there has been broad adoption of body mass index (BMI) as a gold-standard predictor of postoperative complications, yet the lack of consensus on clear BMI cutoffs suggests other factors involved. This study sought to evaluate how comorbidities modify the relationship between BMI and postoperative complications across different surgical locations and define a safe BMI threshold for those with and without comorbidities.

The American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database was filtered for the most common plastic surgery procedures, which were organized by surgical site location. A multivariate logistic regression model was created, which incorporated comorbid status, BMI, and body location as predictors. Simple slopes analysis was performed to assess how the marginal effect of BMI on complication risk varied by comorbidity status within each body location.

A total of 239,676 patients were identified, with 7.1% (n = 17,107) having at least 1 comorbidity and 0.8% (n = 1818) developing postoperative complications. Both BMI and comorbidity were significantly associated with complication development ( P  < 0.01).We noted a significant interaction between the presence of comorbidities and increasing BMI. The combination of comorbidities and elevated BMI is particularly high risk in patients undergoing trunk, breast, and extremity procedures. For patients without comorbidities, BMI <35 kg/m 2 does not significantly increase the risk of complications. In contrast, in patients with comorbid disease, risk of complications begins to increase in patients with a BMI of 30 kg/m 2 .

Through logistic regression analysis of the ACS-NSQIP database, this study demonstrates that elevated BMI alone may not lead to serious postoperative complications until reaching values above 35 or 40 kg/m 2 . Nevertheless, when a comorbidity is present, a BMI of 30 kg/m 2 may be associated with increased risk of complications. This study also shows that BMI-related risks varied by surgical site, with more pronounced complication risk in adipose-rich surgical sites such as the abdomen. It is essential to take a more individualized risk-stratified approach to preoperative patient evaluation with careful consideration of a patient's comorbidities and overall health status.