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Wennberg J, Gittelsohn A. Small area variations in health care delivery.  Science. 1973;182(4117):1102-11084750608PubMedGoogle ScholarCrossref
Fisher ES, Wennberg DE, Stukel TA, Gottlieb DJ, Lucas FL, Pinder EL. The implications of regional variations in Medicare spending, part 1: the content, quality, and accessibility of care.  Ann Intern Med. 2003;138(4):273-28712585825PubMedGoogle ScholarCrossref
Fisher ES, Wennberg DE, Stukel TA, Gottlieb DJ, Lucas FL, Pinder EL. The implications of regional variations in Medicare spending, part 2: health outcomes and satisfaction with care.  Ann Intern Med. 2003;138(4):288-29812585826PubMedGoogle ScholarCrossref
Soumerai SB, McLaughlin TJ, Gurwitz JH,  et al.  Effect of local medical opinion leaders on quality of care for acute myocardial infarction: a randomized controlled trial.  JAMA. 1998;279(17):1358-13639582043PubMedGoogle ScholarCrossref
Coleman JS, Katz E, Menzel H. Medical Innovation: A Diffusion Study. Indianapolis, IN: Bobbs-Merrill; 1966
Barnett ML, Landon BE, O’Malley AJ, Keating NL, Christakis NA. Mapping physician networks with self-reported and administrative data.  Health Serv Res. 2011;46(5):1592-160921521213PubMedGoogle ScholarCrossref
Barnett ML, Christakis NA, O’Malley J, Onnela J-P, Keating NL, Landon BE. Physician patient-sharing networks and the cost and intensity of care in US hospitals.  Med Care. 2012;50(2):152-16022249922PubMedGoogle ScholarCrossref
Dartmouth Medical School Center for the Evaluative Clinical Sciences.  Dartmouth Atlas of Health Care. Chicago, IL: American Hospital Publishing Inc; 1998
Baldwin L-M, Adamache W, Klabunde CN, Kenward K, Dahlman C, Warren LJ. Linking physician characteristics and Medicare claims data: issues in data availability, quality, and measurement.  Med Care. 2002;40(8):(suppl)  IV-82-IV-9512187173PubMedGoogle ScholarCrossref
Pope GC, Kautter J, Ellis RP,  et al.  Risk adjustment of Medicare capitation payments using the CMS-HCCmodel. Accessed December 17, 2010
Ingenix Inc.  What are ETGs? Accessed July 13, 2011
Everett MG, Borgatti SP. Extending centrality. In: Carrington PJ, Scott J, Wasserman S, eds. Models and Methods in Social Network Analysis. New York, NY: Cambridge University Press; 2005
Breiger RL. The duality of persons and groups.  Soc Forces. 1974;53(2):181-190Google Scholar
Wasserman S, Faust K. Network Analysis: Methods and Applications. New York, NY: Cambridge University Press; 1994
Keating NL, Ayanian JZ, Cleary PD, Marsden PV. Factors affecting influential discussions among physicians: a social network analysis of a primary care practice.  J Gen Intern Med. 2007;22(6):794-79817404798PubMedGoogle ScholarCrossref
Newman M. Networks: An Introduction. Oxford, England: Oxford University Press; 2010
Bynum JP, Bernal-Delgado E, Gottlieb D, Fisher E. Assigning ambulatory patients and their physicians to hospitals: a method for obtaining population-based provider performance measurements.  Health Serv Res. 2007;42(1 pt 1):45-6217355581PubMedGoogle ScholarCrossref
Fruchterman TMJ, Reingold EM. Graph drawing by force-directed placement.  Softw Pract Exper. 1991;21(11):1129-1164Google ScholarCrossref
Pham HH, O’Malley AS, Bach PB, Saiontz-Martinez C, Schrag D. Primary care physicians' links to other physicians through Medicare patients: the scope of care coordination.  Ann Intern Med. 2009;150(4):236-24219221375PubMedGoogle ScholarCrossref
Pollack CE, Weissman G, Bekelman J, Liao K, Armstrong K. Physician social networks and variation in prostate cancer treatment in three cities.  Health Serv Res. 2012;47(1 pt 2):380-40322092259PubMedGoogle ScholarCrossref
Iwashyna TJ, Christie JD, Kahn JM, Asch DA. Uncharted paths: hospital networks in critical care.  Chest. 2009;135(3):827-83319265091PubMedGoogle ScholarCrossref
Kinchen KS, Cooper LA, Levine D, Wang NY, Powe NR. Referral of patients to specialists: factors affecting choice of specialist by primary care physicians.  Ann Fam Med. 2004;2(3):245-25215209202PubMedGoogle ScholarCrossref
Barnett ML, Keating NL, Christakis NA, O'Malley AJ, Landon BE. Reasons for choice of referral physician among primary care and specialist physicians [published online September 16, 2011].  J Gen Intern Med. 2012;27(5):506-51221922159PubMedGoogle ScholarCrossref
Keating NL, Zaslavsky AM, Ayanian JZ. Physicians' experiences and beliefs regarding informal consultation.  JAMA. 1998;280(10):900-9049739974PubMedGoogle ScholarCrossref
McPherson M, Smith-Lovin L, Cook JM. Birds of a feather: homophily in social networks.  Annu Rev Sociol. 2001;27(1):415-444Google ScholarCrossref
Apicella CL, Marlowe FW, Fowler JH, Christakis NA. Social networks and cooperation in hunter-gatherers.  Nature. 2012;481(7382):497-50122281599PubMedGoogle ScholarCrossref
Rand DG, Arbesman S, Christakis NA. Dynamic social networks promote cooperation in experiments with humans.  Proc Natl Acad Sci U S A. 2011;108(48):19193-1919822084103PubMedGoogle ScholarCrossref
DesRoches CM, Campbell EG, Rao SR,  et al.  Electronic health records in ambulatory care—a national survey of physicians.  N Engl J Med. 2008;359(1):50-6018565855PubMedGoogle ScholarCrossref
Original Contribution
July 18, 2012

Variation in Patient-Sharing Networks of Physicians Across the United States

Author Affiliations

Author Affiliations: Department of Health Care Policy, School of Medicine (Drs Landon, Keating, Barnett, Paul, O’Malley, Keegan, and Christakis), Department of Biostatistics, School of Public Health (Dr Onnela), and Department of Sociology, Faculty of Arts and Sciences (Dr Christakis), Harvard University, Cambridge and Boston, Massachusetts; Division of Primary Care and General Internal Medicine, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts (Drs Landon and Christakis); and Division of General Internal Medicine, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts (Drs Keating and Barnett).

JAMA. 2012;308(3):265-273. doi:10.1001/jama.2012.7615

Context Physicians are embedded in informal networks that result from their sharing of patients, information, and behaviors.

Objectives To identify professional networks among physicians, examine how such networks vary across geographic regions, and determine factors associated with physician connections.

Design, Setting, and Participants Using methods adopted from social network analysis, Medicare administrative data from 2006 were used to study 4 586 044 Medicare beneficiaries seen by 68 288 physicians practicing in 51 hospital referral regions (HRRs). Distinct networks depicting connections between physicians (defined based on shared patients) were constructed for each of the 51 HRRs.

Main Outcomes Measures Variation in network characteristics across HRRs and factors associated with physicians being connected.

Results The number of physicians per HRR ranged from 135 in Minot, North Dakota, to 8197 in Boston, Massachusetts. There was substantial variation in network characteristics across HRRs. For example, the mean (SD) adjusted degree (number of other physicians each physician was connected to per 100 Medicare beneficiaries) across all HRRs was 27.3 (range, 11.7-54.4); also, primary care physician relative centrality (how central primary care physicians were in the network relative to other physicians) ranged from 0.19 to 1.06, suggesting that primary care physicians were more than 5 times more central in some markets than in others. Physicians with ties to each other were far more likely to be based at the same hospital (69.2% of unconnected physician pairs vs 96.0% of connected physician pairs; adjusted rate ratio, 0.12 [95% CI, 0.12-0.12]; P < .001), and were in closer geographic proximity (mean office distance of 21.1 km for those with connections vs 38.7 km for those without connections, P < .001). Connected physicians also had more similar patient panels in terms of the race or illness burden than unconnected physicians. For instance, connected physician pairs had an average difference of 8.8 points in the percentage of black patients in their 2 patient panels compared with a difference of 14.0 percentage points for unconnected physician pairs (P < .001).

Conclusions Network characteristics vary across geographic areas. Physicians tend to share patients with other physicians with similar physician-level and patient-panel characteristics.