Ask most any health care expert what single factor drives up the nation's healthcare bill unnecessarily, and they'll tell you this: patients who are re-admitted to the hospital within less than 30 days of being discharged.

Now, a report by the Northeast Business Group on Health confirms what those in the field know all too well: It takes a collaborative effort among many stakeholders to reduce those costly trips.

"Hospitals, providers and health plans need to share timely data and take a coordinated approach to care management encompassing pre-admissions and post-discharge care in order to reduce unnecessary hospital readmissions," NEBGH says in its report, "Reducing Hospital Readmissions through Stakeholder Collaboration." More than 1 million Americans wind up back in the hospital only weeks after they left for reasons that could have been prevented — a revolving door that for years has seemed impossible to slow.