The association between outcomes and body mass index in patients with acute respiratory distress syndrome.

Introduction: Limited information exists about the relationship between body mass index (BMI) and the outcome of acute respiratory distress syndrome (ARDS).

Objective: To evaluate the hospital mortality of patients with ARDS in relation to BMI.

Materials And Methods: We conducted a retrospective, multicenter study including patients with ARDS. ARDS was defined according to the Berlin criteria. Body weight and height were obtained to calculate BMI. The primary outcome was in-hospital mortality. Secondary outcomes were intensive care unit (ICU) mortality, invasive positive pressure ventilation (IPPV) free days within 28 days and length of stays in the ICU and hospital.

Results: Among 523 patients, 28 (5%) were underweight (BMI <18.5 kg/m ), 299 (57%) were normal weight (BMI 18.5-24.9 kg/m ), 159 (30%) were overweight (BMI 25-29.9 kg/m ) and 37 (7%) were obese (BMI ≥30 kg/m ). Increasing BMI was associated with younger age (P = 0.017), hypertension (P = 0.003) and diabetes (P = 0.02). Compared with normal weight, being overweight and obese resulted in lower mortality regardless of whether in the hospital (P = 0.019) or ICU (P = 0.044). However, after risk adjustment, only obesity was associated with lower hospital mortality (OR 0.393, 95% CI 0.169-0.914, P = 0.030). With the increase of BMI, the in-hospital mortality and ICU mortality of ARDS dropped gradually (from 57.1% to 24.3%, P = 0.021, and from 53.6% to 24.3%, P = 0.035).

Conclusions: Obesity is associated with lower mortality in patients with ARDS. With the increase of BMI, the mortality of ARDS drops gradually.