Chronic illness with complexity: Implications for performance measurement of optimal glycemic control

OBJECTIVE: To evaluate the association between chronic illness with complexity (CIC) and optimal glycemic control. PARTICIPANTS: Cross-sectional and longitudinal analyses of Diabetes Epidemiologic Cohort database of Veterans Health Administration (VHA) users with diabetes, less than 75 years old, with HbA1c tests in fiscal year (FY) 1999 and 2000, alive at FY2000 end (N = 95,423). DESIGN/MEASUREMENTS: Outcomes were HbA1c < 7% in each FY. CIC included three domains: nondiabetes physical illness, diabetes-related, and mental illness/substance abuse conditions. Other independent variables included age, gender, race, marital status, VHA priority status, and diabetes severity. Longitudinal analyses were restricted to patients with HbA1c ≥ 7% in FY1999 and included hospitalizations between final HbA1c's in FY1999 and FY2000. Multiple logistic regressions examined associations between CIC categories and HbA1c. RESULTS: In FY1999, 33% had HbA1c <7%. In multivariate analyses, patients with nondiabetes physical illness and mental illness/substance abuse were more likely to have HbA1c <7% in FY1999 [adjusted odds ratios for cancer (AOR), 1.31; 95% CI (1.25-1.37); mental illness only, 1.18; 95% CI (1.14-1.22)]. Those with diabetes-related complications were less likely to have HbA1c <7% in FY1999. Associations generally held in FY2000. However, conditions in the mental illness/substance abuse complexity domain were less strongly associated with HbA1c <7%. Macrovascular-related hospitalizations were positively associated with HbA1c <7% [AOR, 1.41; 95% CI (1.34-1.49)]. CONCLUSIONS: The association between CIC and HbA1c <7% is heterogeneous and depends on the domain of complexity. The varying associations of CIC categories with optimal glycemic control suggest the need for appropriate risk adjustment when using HbA1c <7% as a valid performance measure for diabetes quality of care.