Improving the quality of care and expanding insurance coverage can reduce differences in outcomes experienced by different
sociodemographic groups. McWilliams and colleagues used blood pressure, hemoglobin A1c, and total cholesterol measurements obtained from participants in a national survey to measure changes in chronic disease
control. Over 8 years, disease control improved but gaps between white and nonwhite patients did not change. The gaps narrowed
after age 65 years, when universal Medicare insurance begins.