Obesity and pulmonary embolism: the mounting evidence of risk and the mortality paradox.

PURPOSE To determine the prevalence of pulmonary embolism in obese patients according to age, gender and comorbid conditions and explore the relation of obesity to mortality. METHODS The number of patients discharged from short-stay hospitals throughout the United States from 1998-2008 with pulmonary embolism who were obese or not obese, and in-hospital all-cause mortality were determined from the Nationwide Inpatient Sample. RESULTS From 1998-2008, 203,500 of 17,979,200 (1.1%) obese patients were diagnosed with pulmonary embolism compared with 2,034,100 of 346,049,800 (0.6%) non-obese patients [relative risk (RR) =2.03]. Relative risk for pulmonary embolism was highest among obese patients aged 11-20 years (RR=5.80) and was higher in obese women (RR=2.08) than in obese men (RR=1.74). Mortality was 4.3% in obese patients with pulmonary embolism compared with 9.5% in non-obese patients (RR=0.45). Obesity had the greatest effect on mortality in older patients and little effect in teenagers and young adults. Among stable patients who did not receive thrombolytic therapy, mortality was 3.8% in obese patients and 8.4% in non-obese patients (RR=0.45). Among unstable patients, obesity had little effect on mortality. CONCLUSIONS The prevalence of pulmonary embolism in hospitalized patients was higher in obese patients than in non-obese patients. Mortality in patients with pulmonary embolism was lower in obese patients than in non-obese patients, with the greatest effects in women, older patients and stable patients.