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Beyond Volume

Does Hospital Complexity Matter?

An Analysis of Inpatient Surgical Mortality in the United States

McCrum, Marta L., MD, MPH*,†; Lipsitz, Stuart R., ScD*,†; Berry, William R., MD, MPH; Jha, Ashish K., MD, MPH; Gawande, Atul A., MD, MPH*,†

doi: 10.1097/MLR.0000000000000077
Original Articles

Background: Hospitals show wide variation in outcomes and systems of care. It is unclear whether hospital complexity—the range of services and technologies provided—affects outcomes and in what direction. We sought to determine whether complexity was associated with inpatient surgical mortality.

Methods: Using national Medicare data, we identified all fee-for-service inpatients who underwent 1 of 5 common high-risk surgical procedures in 2008–2009 and measured complexity by the number of unique primary diagnoses admitted to each hospital over the 2-year period. We calculated 30-day postoperative mortality rates, adjusting for patient and hospital characteristics, and used multivariable Poisson regression models to test for an association between hospital complexity and mortality rates. We then used this model to generate predicted mortality rates for low-volume and high-volume hospitals across the spectrum of hospital complexity.

Results: A total of 2691 hospitals were analyzed, representing a total of 382,372 admissions. After adjusting for hospital characteristics, including hospital volume, increasing hospital complexity was associated with lower surgical mortality rates. Patients receiving care at the hospitals in the lowest quintile of unique diagnoses had a 27% higher risk of death than those at the highest quintile. The effect of complexity was largest for low-volume hospitals, which were capable of achieving mortality rates similar to high-volume hospitals when in the most complex quintile.

Conclusions: Hospital complexity matters and is associated with lower surgical mortality rates, independent of hospital volume. The effect of complexity on outcomes for nonsurgical services warrants investigation.

*Ariadne Labs: A Joint Center for Health Systems Innovation at Brigham and Women’s Hospital and the Harvard School of Public Health, Harvard School of Public Health

Center for Surgery and Public Health, Brigham and Women’s Hospital

Department of Health Policy and Management, Harvard School of Public Health, Boston, MA

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This study was supported by the Cabot Fellowship from the Center for Surgery and Public Health at Brigham and Women’s Hospital (Dr McCrum) and internal department funds from the Harvard School of Public Health. Dr Gawande reports receiving royalties from publishers, and honoraria for lectures and teaching on improving health systems outcomes (detailed below). There are no conflicts of interest reported by any of the other authors.

Dr Gawande reported receiving royalties from publishers for writing and honoraria from clinical organizations and associations for lectures and teaching on approaches to improving health system outcomes, which can include increasing transparency. In the past 12 months, these publishers and organizations have included the following: Henry Holt, Picador USA, Conde Nast, HarperCollins, Pearson Publishing, Houghton 1 Mifflin, McGraw-Hill, Harvard Business School Press, Profile Books Ltd, New England Journal of Medicine, Penguin Books/India, Sosoh Publishing, Commonwealth Publishing, China Renmin University Press, Lua de Papel, Antoni Bosch Editor, Asa Editore, Editorial Diagonal del Grup62/Edicione, Verlagsgruppe Random House GmbH, Uitgeverij Nieuwezjds, Baronet, Znak, Humanitas, Giulio Einaudi Editore S.p.A., Sextante, Book21, Gramedia Pustaka Utama, Shinyusha Co Ltd, Domingo Publishing, Cheers Publishing, Mehta Publishing House, Misuzu Shobo, Codecs, First News-TriViet Publishing, Cengage Learning, Internazionale Magazine, Eriko Yamauchi, CBS Television, Public Broadcasting Service, TNT Network, Fresenius, National Hospice & Palliative Care Organization, PeaceHealth, Intermountain Health Care, ABT Assoc, Partners Healthcare, American Society of Anesthesiologists, American College of Surgeons, Leading Age, Carolinas Healthcare, University of Albany, American Society of Healthcare Engineers, and University of California at San Francisco.

Reprints: Atul A. Gawande, MD, MPH, Harvard School of Public Health, 677 Huntington Ave., Kresge Building 400, Boston, MA 02115. E-mail:

© 2014 by Lippincott Williams & Wilkins.