The peer-reviewed journal Prehospital Emergency Care includes a paper examining the use of EMS services by DESC supportive housing tenants before and after being housed. In the study University of Washington researchers found an average reduction of 54% in the number of contacts with EMS in the two years after obtaining housing. See:
Housing First is Associated with Reduced Use of Emergency Medical Services – Prehospital Emergency Care (Volume 18 | No.4, October-December 2014)