In the past, evaluating the impact of hospital accreditation was challenging because there was no nationally standardized data. So the Joint Commission and the Centers for Medicare and Medicaid Services (CMS) compared hospitals it accredited with those it didn’t using other evidence-based measures of quality. Those included data that are mandatory to report publicly for common diseases such as heart failure and pneumonia.

From 2004 to 2008, according to a study in the Journal of Hospital Medicine, 8 in 10 accredited U.S. acute care and critical access hospitals outperformed nonaccredited hospitals by these measures.