Mortality association between obesity and pneumonia using a dual restricted cohort model

Background: An obesity survival paradox has been reported among obese patients with pneumonia.

Aims: To determine the impact of obesity on pneumonia outcomes and analyze the correlation between in-hospital all-cause mortality and obesity among patients with pneumonia.

Methods: The United States Nationwide Readmissions Database (NRD) was retrospectively analyzed for patients with pneumonia from 2013 to 2014. We used a step-wise restricted and propensity score matching cohort model (dual model) to compare mortality rates and other outcomes among pneumonia patients based on BMI. Mortality was calculated by a Cox proportional hazard model, adjusted for potential confounders with propensity score matched analysis.

Results: A total of 70,886,775 patients were registered in NRD during the study period. Of these, 7,786,913 patients (11.0%) were considered obese and 1,652,456 patients (2.3%) were admitted to the hospital with pneumonia. Based on the step-wise restricted cohort model, the hazard ratio comparing the mortality rates among obese pneumonia patients to mortality rates among normal BMI pneumonia patients was 0.75 (95% CI 0.60-0.94). The propensity score matched analysis estimated a hazard rate of 0.84 (95% CI 0.79-0.90) and the hazard ratio estimated from the dual model was 0.82 (95% CI 0.63-1.07).

Conclusions: With the application of a dual model, there appears to be no significant difference in mortality of obese patients with pneumonia compared to normal BMI patients with pneumonia.

Keywords: Mortality; Obesity; Pneumonia.