Rationale: Obesity is relatively common among individuals with chronic obstructive pulmonary disease (COPD). However, little is known about the association of obesity with severity of acute exacerbation of COPD and in-hospital mortality.
Objectives: To examine the association of obesity with markers of severity of acute exacerbation of COPD and in-hospital mortality.
Methods: This is a population-based, retrospective cohort study using the 2012-2013 State Inpatient Databases of seven U.S. states (Arkansas, Florida, Iowa, Nebraska, New York, Utah, and Washington). We included adults (aged ≥40 yr) hospitalized for acute exacerbation of COPD. Obesity, use of noninvasive positive pressure ventilation (NIPPV), and use of invasive mechanical ventilation were determined by International Classification of Diseases, Ninth Revision codes. To examine associations between obesity and each outcome (NIPPV, invasive mechanical ventilation, hospital length of stay (LOS), and in-hospital mortality), we fit unadjusted and adjusted logistic regression models using generalized estimating equations to account for patient clustering within hospitals. We adjusted for age, sex, race/ethnicity, primary payer, median household income, patient residence, hospitalization year, chronic comorbidities, and hospital state. In the sensitivity analysis, we used stabilized inverse probability weighting to estimate the causal relation of obesity with outcomes in this observational study.
Results: Of 187,647 patients hospitalized for an acute exacerbation of COPD, 17% were obese. Obesity was associated with increased use of both NIPPV (12.0% vs. 6.5%; adjusted odds ratio [OR] = 1.86; 95% confidence interval [CI] = 1.77-1.95; P < 0.001) and invasive mechanical ventilation (3.5% vs. 2.8%; adjusted OR = 1.13; 95% CI = 1.04-1.22; P = 0.003). Similarly, obese patients were more likely to have a hospital LOS of 4 days or longer (57.9% vs. 50.3%; adjusted OR = 1.37; 95% CI = 1.33-1.41; P < 0.001). In contrast, obesity was associated with a lower in-hospital mortality (0.9% vs. 1.4%; unadjusted OR = 0.63; 95% CI = 0.56-0.72; P < 0.001). After adjusting for potential confounders, this association was no longer statistically significant (adjusted OR = 0.86; 95% CI = 0.75-1.00; P = 0.06). Results were similar in sensitivity analyses using stabilized inverse probability weighting.
Conclusions: In this population-based study of adults hospitalized with an acute exacerbation of COPD, obesity was associated with increased use of noninvasive and invasive ventilation, increased hospital LOS, but was not associated with increased in-hospital mortality.
Keywords: acute exacerbation; chronic obstructive pulmonary disease; hospitalization; mortality; obesity.