In the nested case-control study of patients in the longitudinal cohort with moderately poor control at baseline (HbA1c 8.0-9.0%) matched by age and gender, we found that patients whose HbA1c significantly improved (cases) were less likely to take insulin in 1996 (40.0% vs. 66.0%, p = 0.045), have private insurance or Medicare in 1996 (93.0% vs. 76.6%, p = 0.03), or attend a diabetes specialty clinic (26.5% vs. 46.0%, p = 0.04 in 1996; 34.0% vs. 52.0%, p = 0.06 in 2006) than those whose HbA1c significantly worsened (controls). Here, INS is linked to diabetes mellitus.