Do past mortality rates predict future hospital mortality?

Background: This study aimed to determine whether hospitals with higher historical mortality rates are independently associated with worse patient outcomes.

Methods: Observational study of in-hospital mortality in open abdominal aortic aneurysm repair, aortic valve replacement, and coronary artery bypass graft surgery in a California in-patient database was conducted. Hospitals' annual historical mortality rates between 1998 and 2010 were calculated based on 3 years of data before each year. Results were adjusted for race, sex, age, hospital teaching status, admission year, insurance status, and Charlson comorbidity index.

Results: Hospitals were divided into quartiles based on historical mortality rates. For abdominal aortic aneurysm repair, the odds ratio (OR) of in-hospital mortality for hospitals within the highest quartile of prior mortality was 1.30 compared with the lowest quartile (95% confidence interval [CI] 1.03 to 1.63). For aortic valve replacement, the OR was 1.41 for the 3rd quartile (95% CI 1.15 to 1.73) and 1.54 for the highest quartile (95% CI 1.27 to 1.87). For coronary artery bypass graft surgery, the OR was 1.33 for the 3rd (95% CI 1.2 to 1.49) and 1.58 for the highest (95% CI 1.41 to 1.76) quartiles.

Conclusion: Patients presenting to hospitals with high historical mortality rates have a 30% to 60% increased mortality risk compared with patients presenting to hospitals with low historical mortality rates.