Defining the contribution of chronic kidney disease to all-cause mortality in patients with type 2 diabetes: the Renal insufficiency and cardiovascular events (RIACE) Italian multicenter study

Aims: To define the contribution of chronic kidney disease (CKD) to excess mortality in patients with type 2 diabetes and identify the baseline variables associated with all-cause death in those with and without CKD using the RECursive Partitioning and Amalgamation (RECPAM) method. Methods: This observational, longitudinal, cohort study enrolled 15,773 consecutive non-dialytic patients with type 2 diabetes in 19 Diabetes Clinics throughout Italy in 2006–2008. Based on the presence of albuminuria ≥ 30 mg day−1 and/or estimated glomerular filtration rate (eGFR) < 60 mL min−1·1.73 m−2 at baseline, patients were classified as having or not CKD. Vital status was verified on October 31, 2015 for 99.26% of patients. Results: Mortality increased with increasing albuminuria and eGFR category. Excess risk versus the general population was maximal in patients aged < 55 years in the worse albuminuria or eGFR category. Conversely, in subjects aged ≥ 75 years with albuminuria < 10 mg day−1 or eGFR ≥ 75 mL min−1·1.73 m−2, excess mortality was no longer detectable. At RECPAM analysis, the main correlates of death in the whole cohort were albuminuria > 44 mg day−1, prevalent CVD, and eGFR < ~ 75 mL min−1·1.73 m−2; gender, prevalent CVD, and higher albuminuria in the normoalbuminuric range, in patients without CKD; and CVD, eGFR ~ < 50 mL min−1·1.73 m−2, and albuminuria > 53 mg day−1, in those with CKD. Conclusions: CKD is a major contributor to excess mortality in type 2 diabetes, conferring a very high risk in younger patients and fully accounting for excess risk in the older ones. Higher albuminuria and lower eGFR, even in the normal range, identify individuals with increased mortality risk. Trial registration ClinicalTrials.gov (NCT00715481; https://clinicaltrials.gov/ct2/show/NCT00715481).