Overweight or obese BMI is associated with earlier, but not later survival after common acute illnesses

Abstract

Background

Obesity has been associated with improved short-term mortality following common acute illness, but its relationship with longer-term mortality is unknown.

Methods

Observational study of U.S. Health and Retirement Study (HRS) participants with federal health insurance (fee-for-service Medicare) coverage, hospitalized with congestive heart failure (N = 4287), pneumonia (N = 4182), or acute myocardial infarction (N = 2001), 1996–2012. Using cox proportional hazards models, we examined the association between overweight or obese BMI (BMI ≥ 25.0 kg/m²) and mortality to 5 years after hospital admission, adjusted for potential confounders measured at the same time as BMI, including age, race, sex, education, partnership status, income, wealth, and smoking status. Body mass index (BMI) was calculated from self-reported height and weight collected at the HRS survey prior to hospitalization (a median 1.1 year prior to hospitalization). The referent group was patients with a normal BMI (18.5 to < 25.0 kg/m²).

Results

Patients were a median of 79 years old (IQR 71–85 years). The majority of patients were overweight or obese: 60.3% hospitalized for heart failure, 51.5% for pneumonia, and 61.6% for acute myocardial infarction. Overweight or obese BMI was associated with lower mortality at 1 year after hospitalization for congestive heart failure, pneumonia, and acute myocardial infarction—with adjusted hazard ratios of 0.68 (95% CI 0.59–0.79), 0.74 (95% CI: 0.64–0.84), and 0.65 (95%CI: 0.53–0.80), respectively. Among participants who lived to one year, however, subsequent survival was similar between patients with normal versus overweight/obese BMI.

Conclusions

In older Americans, overweight or obese BMI was associated with improved survival following hospitalization for congestive heart failure, pneumonia, and acute myocardial infarction. This association, however, is limited to the shorter-term. Conditional on surviving to one year, we did not observe a survival advantage associated with excess weight.