Obesity paradox in patients with community-acquired pneumonia: is inflammation the missing link?

Objective Positive associations of body mass index (BMI) and clinical outcomes have been found, called "the obesity paradox". Whether obesity has protective effects or this is due to confounding remains unclear. Herein, we analyzed the effects of weight on long-term mortality in a large cohort of patients with community-acquired pneumonia (CAP) and investigated whether differential effects of obesity on inflammation pathways account for mortality differences. Methods For this secondary analysis, we prospectively followed CAP patients over 6 years previously included in a multicenter trial (“ProHOSP”). To assess associations of BMI with mortality, and with several inflammatory biomarker levels, respectively, we calculated three regression models adjusted for severity (Pneumonia severity index [PSI]), fully-adjusted for PSI, age, gender, metabolic factors, cardiovascular diseases and other comorbidities and fully-adjusted including biomarker levels. Results Within the 763 patients, all-cause 6-year mortality was significantly lower in obese patients (BMI>30kg/m2 ) compared to normal weight patients (BMI18.5-25kg/m2 ) with a severity-adjusted hazard ratio (HR) of 0.641 (95% CI 0.462- to 0.889) and robust results in fully-adjusted and a fully-adjusted plus biomarker models. No associations of increased BMI and C-reactive protein, procalcitonin and white blood cell count were found, but BMI>30Kg/m2 was associated with higher proadrenomedullin levels. Conclusions Over a 6-year long-term follow up we found obesity to be associated with lower all-cause mortality in CAP patients confirming the "obesity paradox" in this population. Yet, differences in inflammatory pathways did not explain these findings.