Background: Although obesity and overweight are associated with increased morbidity and mortality, higher body mass index (BMI) has been shown to be a protective factor from mortality in patients with acute infectious disease, also known as the obesity paradox. However, it is unknown whether these effects persist at long-term follow-up.
Objective: To investigate the relationship between BMI and mortality after hospitalization with an infectious disease in a five-year follow-up period.
Methods: A retrospective analysis of 25,226 adult patients admitted with an acute infectious disease between the years 2010-2020 to Shamir Medical Center, Israel, was conducted. We compared patients in the following BMI categories underweight 15-18.5 kg/m2, normal-weight 18.5-25 kg/m2, overweight 25-30 kg/m2, obesity class-I 30-35 kg/m2, obesity class-II 35-40 kg/m2, and obesity class-III 40-45 kg/m2, regarding mortality during hospitalization and follow-up.
Results: Patients in different BMI categories were heterogeneous regarding baseline demographics and comorbidities, as well as infectious syndrome at index hospitalization. In-hospital mortality and one-year mortality were higher in underweight and normal-weight patients as compared to all other categories, 22% and 13.2% vs. 7-9% (P<0.001) in-hospital, and 31.8% and 20.6% vs. 13-15.6% (P<0.001) at one year. Five-year mortality was only significantly higher in the underweight group, 44.4% vs. 30.8%-36.1% (P<0.001). In a multivariable logistic regression analysis, adjusted for age, sex, comorbidities, and infectious syndrome, underweight was associated with a significantly increased odds ratio (OR) for In-hospital, one-year, and five-year mortality. While, overweight and obesity were associated with a decreased OR for mortality at all time points. Compared to normal-weight OR for mortality at five years was 0.68 (CI 0.62-0.74 P<0.001) in the overweight category, 0.61 (CI 0.55-0.68, P<0.001) in obesity class I, 0.71 (CI 0.61-0.83, P<0.001) in obesity class II, and 0.71 (CI 0.56-0.89, P=0.004) in obesity class III. In a survival analysis model, all categories of obesity were associated with a decreased OR for mortality compared to normal weight, while underweight was associated with increased OR (five-year mortality OR 1.72 CI 1.59-2.07, P<0.001).
Conclusions: Our study found evidence of an obesity paradox for up to five years following hospitalization due to infectious causes. Although we did not find a significant univariate association between BMI of 18.5-25 kg/m2 and five-year mortality, upon multivariate analysis all groups of overweight and obesity were independently associated with decreased mortality compared to this group. Further studies should search for explanations for this counterintuitive phenomenon.
13 May 2023 - 16 May 2023