For minimizing the baseline differences between patients with different body weight, the authors carried out a technique call propensity score (PS)-matched analysis. PS contains 41 variables including demographics, social economic status, chronic comorbidities, and severity of pneumonia. Patients were matched 1:1:1 using this technique across the three groups of normal weight, overweight and obese. The authors then used computer modeling on the PS-matched pairs to assess the association between body weight and 30-day in-hospital mortality.
A total of 1,690,760 pneumonia hospitalization episode fulfilled the inclusion criteria, of which 17,992 were overweight, 195,889 were obese, and 1,476,879 were normal weight. To investigate whether there was a differential risk of 30- day mortality among different obese populations, the authors stratified patients into different subgroups and adjust the risk for mortality using PS score.
- Compared with normal weight patients without the use of ventilator, overweight patients were 23% more likely to survive and obese patients 29% more likely to survive.
- Similar results were obtained in the cohort of more serious pneumonia requiring the use of ventilator overweight and obese patients were 21% and 30% respectively more likely to survive than normal weight patients.
- the survival benefit of obesity is consistent in all subgroups, patients with lower comorbidity burden/severity had substantially better survival.
- being in the lowest co-morbidity quartile compared with the highest is associated with 53% improvement in survival, and being in the group with the lowest severity of pneumonia was associated with 67% improvement in survival compared with the highest severity.
“Using a large and nationally representative sample of over 1,000 hospitals in the US, we found that increase in body mass index was significantly associated with improved survival in patients hospitalized with pneumonia. We also found that severity and comorbidity burden had a modifying effect on survival, concluded the authors.