No obesity paradox in patients with community-acquired pneumonia - secondary analysis of a randomized controlled trial

Abstract

Background: Obesity is associated with an increased risk for several chronic conditions and mortality. However, there are data in support of beneficial outcome in acute medical conditions such as community-acquired pneumonia (CAP), termed "obesity paradox". The aim of this study was to test the association of BMI with clinical outcomes in a large randomized clinical trial of patients hospitalized with CAP.

Design and methods: In total, 773 patients hospitalized with CAP were included in this study. Patients were stratified into four groups according to their baseline BMI (underweight <18.5, normal weight 18.5-25, overweight 25-30, and obese >30 kg/m²). The primary endpoint was time to clinical stability (TTCS). Secondary endpoints included 30-day mortality, ICU admission rate, CAP complications, and duration of antibiotic treatment.

Results: BMI and TTCS had a U-shaped association with shortest TTCS among patients at an overweight BMI of 28 kg/m². In patients with obesity, there was a trend towards reduced hazards to reach clinical stability when compared to patients with normal weight (HR 0.82; 95%CI, 0.67-1.02; p = 0.07). In underweight BMI group TTCS was prolonged by 1 day (HR 0.63; 95%CI, 0.45-0.89; p = 0.008). There was no difference in mortality or ICU admission rates between BMI groups (p > 0.05). While in the underweight BMI group the total duration of antibiotic treatment was prolonged by 2.5 days (95%CI, 0.88-4.20, p = 0.003), there was no difference in patients with obesity.

Conclusions: The overweight BMI group had shortest time to clinical stability. While underweight patients face adverse clinical outcomes, there is neither beneficial, nor adverse outcome in patients with obesity hospitalized for CAP.

Clinicaltrials: gov (registration no. NCT00973154).

Fig. 1. BMI and time to clinical stability.

Fractional polynomial estimation of the association of BMI with the time to clinical stability (TTCS) (blue curve) along with the confidence interval of the mean (gray area). There is a U-shaped association between TTCS and BMI.

Fig. 2. BMI and length of hospital stay.

Fractional polynomial estimation of the association of BMI with the length of hospital stay (LOS) (blue curve) along with the confidence interval of the mean (gray area). There is a U-shaped association between LOS and BMI.