The Impact of Cardiovascular Disease and Chronic Kidney Disease on Life Expectancy and Direct Medical Cost in a 10-Year Diabetes Cohort Study

Abstract

OBJECTIVE The relative effects of various cardiovascular diseases (CVDs) and varying severity of chronic kidney disease (CKD) on mortality risk, direct medical cost, and life expectancy in patients with diabetes are unclear. The aim of this study was to evaluate these associations. RESEARCH DESIGN AND METHODS This was a retrospective cohort study that included 208,792 adults with diabetes stratified into 12 disease status groups with varying combinations of heart disease, stroke, moderate CKD (estimated glomerular filtration rate [eGFR] 30–59 mL/min/1.73 m2) and severe CKD (eGFR <30 mL/min/1.73 m2) in 2008–2010. The effect of risk of mortality, annual direct medical costs, and life expectancy were assessed using Cox regression, gamma generalized linear method with log-link function, and flexible parametric survival models. RESULTS Over a median follow-up of 8.5 years (1.6 million patient-years), 50,154 deaths were recorded. Mortality risks for patients with only a single condition among heart disease, stroke, and moderate CKD were similar. The mortality risks were 1.75 times, 2.63 times, and 3.58 times greater for patients with one, two, and all three conditions (consisting of stroke, heart disease, and moderate CKD), compared with patients without these diseases, suggesting an independent and individually additive effect for any combination. A similar trend was observed in annual public health care costs with 2.91-, 3.90-, and 3.88-fold increased costs for patients with one, two, and three conditions, respectively. Increases in the number of conditions reduced life expectancy greatly, particularly in younger patients. Reduction in life expectancy for a 40-year-old with one, two, and three conditions was 20, 25, and 30 years for men and 25, 30, and 35 years, respectively, for women. A similar trend of greater magnitude was observed for severe CKD. CONCLUSIONS The effects of heart diseases, stroke, CKD, and the combination of these conditions on all-cause mortality and direct medical costs are independent and cumulative. CKD, especially severe CKD, appears to have a particularly significant impact on life expectancy and direct medical costs in patients with diabetes. These findings support the importance of preventing both CVD and CKD in patients with diabetes.