Abstract
BackgroundObesity has been associated with improved short-term mortality following common acute illness, but its relationship with longer-term mortality is unknown.MethodsObservational 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).ResultsPatients 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.ConclusionsIn 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.
Highlights
Obesity has been associated with improved short-term mortality following common acute illness, but its relationship with longer-term mortality is unknown
congestive heart failure (CHF), pneumonia, and acute myocardial infarction (AMI) hospitalizations We identified 4287 CHF hospitalizations, 4182 pneumonia hospitalizations, and 2001 AMI hospitalizations for inclusion in the study (Additional file 1: Figure S1, Table 1)
Adjusted HR for 1-year mortality were 0.70, 0.77, and 0.67 after CHF, pneumonia, and AMI hospitalization, respectively
Summary
Obesity has been associated with improved short-term mortality following common acute illness, but its relationship with longer-term mortality is unknown. After careful control for potential confounders, a recent study found the risk of mortality increases steeply with BMIs of 27 and higher [16]. Understanding the long-term association of obesity on survival after acute hospitalization is important to guiding weight control recommendations. Patients’ weights are generally obtained after hospital admission [17, 18], when they may be biased by acute fluid shifts. This practice may misclassify body mass index (BMI) category in as many as 20% of patients [19]. Many studies examine in-hospital mortality, which may be biased by discharge to nursing and long-term acute care facilities [20]. Discharge practices could plausibly be different for obese patients, who typically require more intensive nursing care for a given level of illness
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