title: Spatial analysis of elderly access to primary care services.
abstract: BACKGROUND
  Admissions for Ambulatory Care Sensitive Conditions (ACSCs) are considered preventable admissions, because they are unlikely to occur when good preventive health care is received. Thus, high rates of admissions for ACSCs among the elderly (persons aged 65 or above who qualify for Medicare health insurance) are signals of poor preventive care utilization. The relevant geographic market to use in studying these admission rates is the primary care physician market. Our conceptual model assumes that local market conditions serving as interventions along the pathways to preventive care services utilization can impact ACSC admission rates.
  
  
  RESULTS
  We examine the relationships between market-level supply and demand factors on market-level rates of ACSC admissions among the elderly residing in the U.S. in the late 1990s. Using 6,475 natural markets in the mainland U.S. defined by The Health Resources and Services Administration's Primary Care Service Area Project, spatial regression is used to estimate the model, controlling for disease severity using detailed information from Medicare claims files. Our evidence suggests that elderly living in impoverished rural areas or in sprawling suburban places are about equally more likely to be admitted for ACSCs. Greater availability of physicians does not seem to matter, but greater prevalence of non-physician clinicians and international medical graduates, relative to U.S. medical graduates, does seem to reduce ACSC admissions, especially in poor rural areas.
  
  
  CONCLUSIONS
  The relative importance of non-physician clinicians and international medical graduates in providing primary care to the elderly in geographic areas of greatest need can inform the ongoing debate regarding whether there is an impending shortage of physicians in the United States. These findings support other authors who claim that the existing supply of physicians is perhaps adequate, however the distribution of them across the landscape may not be optimal. The finding that elderly who reside in sprawling urban areas have access impediments about equal to residents of poor rural communities is new, and demonstrates the value of conceptualizing and modelling impedance based on place and local context.
authors.affiliation: RTI International, 275 Cox, 3040 Cornwallis Road, Research Triangle Park, NC 27709-2194, USA. lmobley@rti.org
authors.forename: Lee R
authors.initials: LR
authors.lastname: Mobley
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Root
authors.forename: Luc
authors.initials: L
authors.lastname: Anselin
authors.forename: Nancy
authors.initials: N
authors.lastname: Lozano-Gracia
authors.forename: Julia
authors.initials: J
authors.lastname: Koschinsky
mesh_terms: D000368:Aged; D006301:Health Services Needs and Demand / Q000191:economics; D006299:Health Services for the Aged / Q000191:economics / Q000706:statistics & numerical data*; D006760:Hospitalization / Q000191:economics / Q000706:statistics & numerical data*; D006801:Humans; D017146:Models, Organizational; D011314:Preventive Health Services / Q000191:economics / Q000706:statistics & numerical data*; D011320:Primary Health Care / Q000191:economics / Q000706:statistics & numerical data; D012189:Retrospective Studies; D012959:Socioeconomic Factors; D014481:United States