title: Decomposing racial/ethnic disparities in influenza vaccination among the elderly.
abstract: While persistent racial/ethnic disparities in influenza vaccination have been reported among the elderly, characteristics contributing to disparities are poorly understood. This study aimed to assess characteristics associated with racial/ethnic disparities in influenza vaccination using a nonlinear Oaxaca-Blinder decomposition method. We performed cross-sectional multivariable logistic regression analyses for which the dependent variable was self-reported receipt of influenza vaccine during the 2010-2011 season among community dwelling non-Hispanic African-American (AA), non-Hispanic White (W), English-speaking Hispanic (EH) and Spanish-speaking Hispanic (SH) elderly, enrolled in the 2011 Medicare Current Beneficiary Survey (MCBS) (un-weighted/weighted N=6,095/19.2 million). Using the nonlinear Oaxaca-Blinder decomposition method, we assessed the relative contribution of seventeen covariates - including socio-demographic characteristics, health status, insurance, access, preference regarding healthcare, and geographic regions - to disparities in influenza vaccination. Unadjusted racial/ethnic disparities in influenza vaccination were 14.1 percentage points (pp) (W-AA disparity, p<0.001), 25.7 pp (W-SH disparity, p<0.001) and 0.6 pp (W-EH disparity, p>.8). The Oaxaca-Blinder decomposition method estimated that the unadjusted W-AA and W-SH disparities in vaccination could be reduced by only 45% even if AA and SH groups become equivalent to Whites in all covariates in multivariable regression models. The remaining 55% of disparities were attributed to (a) racial/ethnic differences in the estimated coefficients (e.g., odds ratios) in the regression models and (b) characteristics not included in the regression models. Our analysis found that only about 45% of racial/ethnic disparities in influenza vaccination among the elderly could be reduced by equalizing recognized characteristics among racial/ethnic groups. Future studies are needed to identify additional modifiable characteristics causing disparities in influenza vaccination.
authors.affiliation: Department of Public Health Sciences, University of California Davis School of Medicine, One Shields Ave. Medical Sciences 1C, Davis, CA 95616, USA. Electronic address: byoo@ucdavis.edu.
authors.forename: Byung-Kwang
authors.initials: BK
authors.lastname: Yoo
authors.affiliation: Department of Public Health Sciences, University of California Davis School of Medicine, One Shields Ave. Medical Sciences 1C, Davis, CA 95616, USA; Faculty of Liberal Arts, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554, Japan. Electronic address: thasebe@sophia.ac.jp.
authors.forename: Takuya
authors.initials: T
authors.lastname: Hasebe
authors.affiliation: Department of Pediatrics, University of California Los Angeles (UCLA), LeConte Avenue, Los Angeles, CA 10833, USA. Electronic address: pszilagyi@mednet.ucla.edu.
authors.forename: Peter G
authors.initials: PG
authors.lastname: Szilagyi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D005006:Ethnicity; D005260:Female; D006299:Health Services for the Aged; D054625:Healthcare Disparities / Q000208:ethnology / Q000706:statistics & numerical data; D006801:Humans; D007252:Influenza Vaccines / Q000008:administration & dosage*; D007251:Influenza, Human / Q000517:prevention & control; D016015:Logistic Models; D008875:Middle Aged; D016017:Odds Ratio; D013997:Time Factors; D014611:Vaccination / Q000706:statistics & numerical data*
chemical_list: D007252:Influenza Vaccines
keywords: Elderly population; Influenza vaccination; Non-linear Oaxaca–Blinder decomposition method; Racial/ethnic disparities