Comorbidity and glycemic control in patients with type 2 diabetes

Background: It is commonly believed that good glycemic control is hard to achieve in patients with diabetes mellitus and concurrent chronic illnesses. Objective: To determine the impact of comorbidity on glycemic control at presentation and subsequent follow-up in patients with type 2 diabetes. Methods: We studied 654 consecutive patients who presented to a diabetes clinic in 1997. Comorbidity was rated using the Chronic Disease Score (CDS) index, which is a validated, weighted score that takes into account the patient's age, sex, and classes of medications. Univariate and multivariate linear regressions were used to determine the contribution of age, body mass index (calculated as weight in kilograms divided by the square of height in meters), diabetes duration, type of therapy, and CDS to initial hemoglobin A_1c (HbA_1c) level. A similar analysis was performed for the 169 patients with follow-up HbA_1c levels 6 months after presentation. Results: Patients were 90% African American, and 66% female, with average age of 53 years. Average diabetes duration was 5 years; body mass index, 33; HbA_1c level, 8.8%; and CDS, 1121 (range, 232-7953). At presentation, patients with higher CDSs tended to be older and to have a lower HbA_1c level, but multivariate linear regression showed that receiving pharmacological therapy, younger age, and having a lower C-peptide level were the only significant contributors to HbA_1c level. In the 169 follow-up patients, presenting characteristics were not significantly different from those of the full cohort: average initial HbA_1c level was 8.8%; CDS, 1073. Their HbA_1c level at 6 months averaged 7.5% and the CDS had no significant impact on their follow-up HbA_1c level. Conclusion: Comorbidity does not appear to limit achievement of good glycemic control in patients with type 2 diabetes.