Adapted Diabetes Complications Severity Index and Charlson Comorbidity Index in predicting all-cause and cause-specific mortality among patients with type 2 diabetes

Introduction Adapted Diabetes Complications Severity Index (aDCSI) is a commonly used severity measure based on the number and severity of diabetes complications using diagnosis codes. The validity of aDCSI in predicting cause-specific mortality has yet to be verified. Additionally, the performance of aDCSI in predicting patient outcomes compared with Charlson Comorbidity Index (CCI) remains unknown. Research design and methods Patients aged 20 years or older with type 2 diabetes prior to January 1, 2008 were identified from the Taiwan National Health Insurance claims data and were followed up until December 15, 2018. Complications for aDCSI including cardiovascular, cerebrovascular and peripheral vascular disease, metabolic disease, nephropathy, retinopathy and neuropathy, along with comorbidities for CCI, were collected. HRs of death were estimated using Cox regression. Model performance was evaluated by concordance index and Akaike information criterion. Results 1,002,589 patients with type 2 diabetes were enrolled, with a median follow-up of 11.0 years. After adjusting for age and sex, aDCSI (HR 1.21, 95% CI 1.20 to 1.21) and CCI (HR 1.18, 1.17 to 1.18) were associated with all-cause mortality. The HRs of aDCSI for cancer, cardiovascular disease (CVD) and diabetes mortality were 1.04 (1.04 to 1.05), 1.27 (1.27 to 1.28) and 1.28 (1.28 to 1.29), respectively, and the HRs of CCI were 1.10 (1.09 to 1.10), 1.16 (1.16 to 1.17) and 1.17 (1.16 to 1.17), respectively. The model with aDCSI had a better fit for all-cause, CVD and diabetes mortality with C-index of 0.760, 0.794 and 0.781, respectively. Models incorporating both scores had even better performance, but the HR of aDCSI for cancer (0.98, 0.97 to 0.98) and the HRs of CCI for CVD (1.03, 1.02 to 1.03) and diabetes mortality (1.02, 1.02 to 1.03) became neutral. When aDCSI and CCI were considered time-varying scores, the association with mortality was stronger. aDCSI had a strong correlation with mortality even after 8 years (HR 1.18, 1.17 to 1.18). Conclusions The aDCSI predicts all-cause, CVD and diabetes deaths but not cancer deaths better than the CCI. aDCSI is also a good predictor for long-term mortality.