title: Physician impact on hospital admission and on mortality rates in the Medicare population.
abstract: OBJECTIVE
  We assess the effect of variations in the supply and specialty distribution of physicians on admission rates for ambulatory care-sensitive conditions (ACS) and for all causes, and on mortality rates among Medicare beneficiaries of various health care service areas (HCSA).
  
  
  METHODS
  For the Medicare beneficiaries, sources were the Health Care Financing Administration's 1992 enrollment and impatient (Part A) files for a 5 percent sample of that population; for the overall populations and for the medical resources of the HCSAs, the Area Resource File.
  
  
  METHODS
  This observational, cross-sectional study employed multiple linear regression to assess the influence of population characteristics and of the supply of physicians on hospital admissions, and Poisson regression in the analysis of the factors that affect mortality.
  
  
  RESULTS
  Physician supply levels vary nearly fourfold or more when comparing the top and bottom deciles of the HCSAs, Medicare admissions for ACS conditions vary about threefold, and admission rates for all causes and mortality rates vary about 1.5-fold. Physician supply levels and distributions have very little influence on ACS admission rates, and even less on the admissions for all causes and on mortality, except in HCSAs with very low physician supply levels (one-fourth the national average or less). However, these HCSAs account for only about 1 percent of the U.S. population.
  
  
  CONCLUSIONS
  Physician supply levels and the proportions of specialists and generalists have negligible effects on health status as measured by mortality rates and by rates of admission for all causes and for conditions presumed to be sensitive to the adequacy of ambulatory care. Reductions in admissions for such conditions are not likely to be achieved through broadening of insurance to levels that exist under Medicare, nor through increases in the supply of physicians, nor, conversely, through a reduction in any presumed oversupply of physicians.
authors.affiliation: Department of Preventive Medicine and Biometrics, Uniformed Services University of the Health Sciences, School of Medicine, Bethesda, MD 20814-4799, USA.
authors.forename: H
authors.initials: H
authors.lastname: Krakauer
authors.forename: I
authors.initials: I
authors.lastname: Jacoby
authors.forename: M
authors.initials: M
authors.lastname: Millman
authors.forename: J E
authors.initials: JE
authors.lastname: Lukomnik
mesh_terms: D000368:Aged; D000553:Ambulatory Care / Q000639:trends; D002391:Catchment Area, Health / Q000706:statistics & numerical data; D014487:Centers for Medicare and Medicaid Services, U.S.; D003430:Cross-Sectional Studies; D003710:Demography; D005260:Female; D006299:Health Services for the Aged / Q000706:statistics & numerical data* / Q000639:trends; D006280:Health Workforce; D006801:Humans; D008297:Male; D006278:Medicare / Q000706:statistics & numerical data*; D009026:Mortality; D010343:Patient Admission / Q000706:statistics & numerical data* / Q000639:trends; D010820:Physicians / Q000600:supply & distribution*; D010818:Practice Patterns, Physicians' / Q000706:statistics & numerical data*; D012044:Regression Analysis; D013038:Specialization; D014481:United States / Q000453:epidemiology