Sodium to creatinine ratio in spot urine is associated with heart failure hospitalization in Japanese high-risk patients

Our previous study [Evaluation of sodium intake for the prediction of cardiovascular events in Japanese high-risk patients (ESPRIT study)] reported that increased sodium excretion ≥4.0 g/day was associated with composite cardiovascular events in hospitalization for heart failure (HF), acute coronary syndrome, cerebrovascular events and documented cardiovascular-related mortality in Japanese high-risk patients with either stable and compensated HF, coronary artery disease, cerebrovascular disease, chronic kidney disease or atrial fibrillation. However, the method of estimating sodium excretion levels using spot urine is complex, requiring age, body weight, height and multiplier factors for calculation. The aim of the present study was to elucidate whether the sodium to creatinine ratio in spot urine, a key component in estimating daily sodium excretion, was associated with hospitalization for HF. The present study performed a post-hoc analysis of the ESPRIT study (n=520; 60 hospitalizations for HF). Receiver operating curve analysis yielded an optimal sodium to creatinine ratio cut-off value of 24.8 for detecting hospitalization for HF. Kaplan-Meier curve analysis revealed that a high sodium to creatinine ratio in spot urine was associated with an increased hospitalization for HF (P<0.001). Cox regression analysis revealed that a high sodium to creatinine ratio was associated with hospitalization for HF with a hazard ratio (HR) of 2.49 [95% confidence interval (95% CI), 1.47-4.16]. Following adjustment for age, sex and body weight, the HR was as high as 2.74 (95% CI, 1.51-4.71). This association remained following further adjustment for brain natriuretic peptide, estimated glomerular filtration rate, diabetes mellitus or the use of diuretics. Overall, the present study demonstrated that the sodium to creatinine ratio in spot urine is associated with hospitalization for HF in Japanese high-risk patients.