Urinary Potassium Excretion and Renal and Cardiovascular Complications in Patients with Type 2 Diabetes and Normal Renal Function.

BACKGROUND AND OBJECTIVES We investigated the association of urinary potassium and sodium excretion with the incidence of renal failure and cardiovascular disease in patients with type 2 diabetes. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS A total of 623 Japanese type 2 diabetic patients with eGFR≥60 ml/min per 1.73 m(2) were enrolled in this observational follow-up study between 1996 and 2003 and followed-up until 2013. At baseline, a 24-hour urine sample was collected to estimate urinary potassium and sodium excretion. The primary end point was renal and cardiovascular events (RRT, myocardial infarction, angina pectoris, stroke, and peripheral vascular disease). The secondary renal end points were the incidence of a 50% decline in eGFR, progression to CKD stage 4 (eGFR<30 ml/min per 1.73 m(2)), and the annual decline rate in eGFR. RESULTS During the 11-year median follow-up period, 134 primary end points occurred. Higher urinary potassium excretion was associated with lower risk of the primary end point, whereas urinary sodium excretion was not. The adjusted hazard ratios for the primary end point in Cox proportional hazards analysis were 0.56 (95% confidence interval [95% CI], 0.33 to 0.95) in the third quartile of urinary potassium excretion (2.33-2.90 g/d) and 0.33 (95% CI, 0.18 to 0.62) in the fourth quartile (>2.90 g/d) compared with the lowest quartile (<1.72 g/d). Similar associations were observed for the secondary renal end points. The annual decline rate in eGFR in the fourth quartile of urinary potassium excretion (-1.3 ml/min per 1.73 m(2)/y; 95% CI, -1.5 to -1.0) was significantly slower than those in the first quartile (-2.2; 95% CI, -2.4 to -1.8). CONCLUSIONS Higher urinary potassium excretion was associated with the slower decline of renal function and the lower incidence of cardiovascular complications in type 2 diabetic patients with normal renal function. Interventional trials are necessary to determine whether increasing dietary potassium is beneficial.