Residential Segregation and the Availability of Primary Care Physicians

Research Objective: To examine the association between residential segregation and geographic access to primary care physicians.

Study Design: Using data from the 2006 American Medical Association master file and the 2000 Census, we computed the population to primary care physician (PCP) ratio for each zip code in a metropolitan statistical area (MSA). We defined PCP shortage areas as those zip codes with no PCP or a population to PCP ratio of greater than 3500. We estimated the association between whether a zip code was a PCP shortage area and the minority composition of the zip code and degree of segregated in the zip code's MSA. Minority composition was measured by indicator variables that denoted whether the zip code was predominately (50% or more) African American, predominately Hispanic, or predominately Asian. We used the Census Bureau's MSA measures of segregation. Five segregation measures for each minority group were considered: dissimilarity index, isolation index, spatial/clustering index, centralization index and concentration index. In the logistic regression, we controlled for distribution of the population by age, gender, poverty status, education attainment, and home ownership in the zip code.

Population Studied: Our sample consists of 15,900 zip codes located partially or completely in an MSA or which 15801 have segregation data for each minority group. Of these zip codes, 4.9% were predominately African American, 4.4% were predominately Hispanic, and 0.2% were predominately Asian.

Principal Findings: Overall we found that predominately African American zip codes were more likely to be a PCP shortage area (OR = 1.65 p = 0.001). However, this relationship varies with the degree of segregation in the MSA. As segregation measured by the dissimilarity index, centralization index and concentration index increased the odds of being a PCP shortage area increased for African American zip codes. The odd ratios for low segregation area ranged from 0.96 to 1.23 compared to high segregation areas which ranged from 2.16 to 2.70. We found that when the clustering index for Asian was included in the model, the predominately Asian zip codes in low segregation areas were more likely to be PCP shortage areas (OR=3.43) compared to high segregation areas (OR = 0.93). We did not find an association between predominately Hispanic zip codes and PCP shortage areas.

Conclusions: Efforts should be made to improve geographic access to PCPs in African American communities in segregated MSAs and Asian communities in low segregated MSAs.