Sodium, potassium intake and urinary sodium-to-potassium ratio in rheumatoid arthritis: association with markers of cardiovascular dysfunction and disease-related parameters.

INTRODUCTION/

OBJECTIVES

Patients with rheumatoid arthritis (RA) are at increased cardiovascular risk. Rather than either sodium or potassium intake alone, the ratio of urinary sodium-to-potassium excretion has been introduced as a simple and useful indicator of diet quality and a more reliable index of cardiovascular risk assessment. We assessed the clinical impact of sodium-to-potassium ratio as a marker of cardiovascular health in patients with RA.

METHOD: Sodium and potassium intake were assessed from 24-h urine samples, and urinary sodium-to-potassium ratio was calculated in patients with RA. Myocardial perfusion was assessed by measurement of subendocardial viability ratio (SEVR) using applanation tonometry. Pulse wave velocity and augmentation index were assessed as markers of arterial stiffness with the same device.

RESULTS

Among 61 patients with RA, only two presented an optimal sodium-to-potassium ratio of ≤ 1. In univariate analysis, urinary sodium excretion was significantly associated with high-density lipoprotein cholesterol (HDL-c) and uric acid. Potassium excretion positively correlated with estimated glomerular filtration rate (eGFR) and negatively with disease activity and inflammatory load. No associations were observed between markers of arterial stiffness and either urinary sodium excretion, potassium excretion, or their ratio. By contrast, both urinary sodium and urinary sodium-to-potassium ratio inversely correlated with SEVR, and these associations remained significant even after adjustment for other variables (beta =  - 0.247, p = 0.034, and beta =  - 0.247, p = 0.026, respectively).

CONCLUSIONS

Findings from the present study suggest that in concordance with population-based studies, urinary sodium-to-potassium ratio might serve as an indicator of myocardial health in patients with autoimmune inflammatory diseases such as RA. Key Points • Increased dietary sodium intake, decreased dietary potassium intake, and increased sodium-to-potassium ratio have been associated with adverse cardiovascular outcomes in longitudinal population-based cohorts. • In a population of high cardiovascular risk patients with RA, increased dietary sodium intake and increased urinary sodium-to-potassium ratio were both associated with impaired coronary microvascular perfusion. • Dietary potassium intake inversely correlated with disease activity and inflammatory load. • In patients with chronic inflammatory arthritis, interventions aiming at dietary modifications of sodium and potassium intake might positively affect both cardiovascular outcomes and disease-related parameters.