Effect of Electronic Health Records on Health Care Costs: Longitudinal Comparative Evidence From Community Practices

adoption of electronic health records (EHRs) but lacks robust em-pirical evidence to anticipate the effect on health care costs. Objective: To assess short-term cost savings from community-wide adoption of ambulatory EHRs. Design: Longitudinal trial with parallel control group. Setting: Natural experiment in which 806 ambulatory clinicians across 3 Massachusetts communities adopted subsidized EHRs. Six matched control communities applied but were not selected to participate. Patients: 47 979 intervention patients and 130 603 control patients. Measurements: Monthly standardized health care costs from com-mercial claims data from January 2005 to June 2009, including total cost, inpatient cost, and ambulatory cost and its subtypes (phar-macy, laboratory, and radiology). Projected savings per member pe