INS and diabetes mellitus: In an analysis with multiple linear regression, we found that city residency (p = 0.001), a high education level (p < 0.001), employment status (p = 0.005), monthly income (p < 0.001), longer duration of DM (p < 0.001) and no insulin use (p < 0.001) were significantly associated with a better score on the MDKT test (Table 9).