Socioeconomic and Physician Supply Determinants of Racial Disparities in Colorectal Cancer Screening

Purpose: Causes of racial disparities in colorectal cancer (CRC) screening may extend beyond individual-level characteristics. We examined how physician density, beyond socioeconomic factors, affected observed racial disadvantages in recent CRC screening for blacks and Hispanics. Methods: We obtained socioeconomic and CRC screening information on adults age >= 50 years from the Behavioral Risk Factor Surveillance System (1997 to 2008) and information on the number of primary care physicians and gastroenterologists from the American Medical Association Masterfile (1997 to 2008). We used fixed-effect multivariate logistic regression to model the probability of receiving a fecal occult blood test within the past year or endoscopic screening within the past 5 years as a function of individual-level socioeconomic factors and state-level physician supply. Results: In 2008, 60.6% of whites were current on CRC screening (95% CI, 60.6% to 61.0%) compared with 57.9% of blacks (95% CI, 56.7% to 59.2%) and 42.9% of Hispanics (95% CI, 41.0% to 44.8%). Inclusion of socioeconomic variables reversed black-white disparities (odds ratio [OR], 1.17; 95% CI, 1.15 to 1.19) but did not explain disadvantage for Hispanics (OR, 0.89; 95% CI, 0.87 to 0.92). Once interaction of race and physician supply was considered, likelihood of recent CRC screening became statistically indistinguishable for Hispanics and whites of similar socioeconomic status residing in states with high physician supplies. Conclusion: Socioeconomic factors and physician supply are key predictors of CRC screening. Adjustment for socioeconomic determinants explained black-white disparities; further adjustment for physician supply explained Hispanic-white disparities. Physician distribution is a potentially remediable contributor to ethnic/racial disparities in CRC screening. Whether the United States is able to equitably meet future demand for screening may depend on access, physician supply, and organization of the health care system.