Table 3.

Rate of death according to serum potassium by eGFR stratum

VariableSerum K+ Level Omnibus P Value
<3.5 mEq/L3.5–3.9 mEq/L4.0–4.4 mEq/L4.5–4.9 mEq/L5.0–5.4 mEq/L5.5–5.9 mEq/L≥6.0 mEq/L
eGFR<30 ml/min per 1.73 m2
 Deaths, n32942122771756339
 Patient-years126726221131602121699164
 Crude ratea (95% CI) 0.26 (0.18 to 0.36)0.13 (0.11 to 0.16)0.10 (0.08 to 0.11)0.09 (0.08 to 0.10)0.08 (0.07 to 0.10)0.09 (0.07 to 0.12)0.24 (0.18 to 0.32)
 Adjusted IRRb,c (95% CI)2.77 (1.89 to 4.06)1.30 (1.02 to 1.66)1.05 (0.87 to 1.26)Ref1.01 (0.83 to 1.22)1.11 (0.84 to 1.47)3.08 (2.17 to 4.37)<0.001
eGFR 30–39 ml/min per 1.73 m2
 Deaths, n35130297310152508
 Patient-years2251681569469843636873137
 Crude ratea (95% CI) 0.16 (0.11 to 0.22)0.08 (0.07 to 0.09)0.05 (0.05 to 0.06)0.04 (0.04 to 0.05)0.04 (0.04 to 0.05)0.06 (0.04 to 0.08)0.06 (0.03 to 0.12)
 Adjusted IRRb,d (95% CI)4.31 (2.36 to 7.89)1.08 (0.68 to 1.69)0.90 (0.64 to 1.25)Ref0.73 (0.47 to 1.11)0.98 (0.52 to 1.88)2.74 (1.13 to 6.74)0.04
eGFR 40–49 ml/min per 1.73 m2
 Deaths, n29142391354171446
 Patient-years486384512,79613,61254551018127
 Crude ratea (95% CI) 0.06 (0.04 to 0.09)0.04 (0.03 to 0.04)0.03 (0.03 to 0.03)0.03 (0.02 to 0.03)0.03 (0.03 to 0.04)0.04 (0.03 to 0.06)0.05 (0.02 to 0.11)
 Adjusted IRRb,c (95% CI)2.52 (1.71 to 3.71)1.46 (1.19 to 1.78)1.16 (1.00 to 1.34)Ref1.18 (0.99 to 1.42)1.68 (1.23 to 2.30)1.72 (0.76 to 3.86)0.001
eGFR 50–59 ml/min per 1.73 m2
 Deaths, n57277612469170367
 Patient-years974955430,34926,23087011316117
 Crude ratea (95% CI) 0.06 (0.05 to 0.08)0.03 (0.03 to 0.03)0.02 (0.02 to 0.02)0.02 (0.02 to 0.02)0.02 (0.02 to 0.02)0.03 (0.02 to 0.04)0.06 (0.03 to 0.13)
 Adjusted IRRb,d (95% CI)4.15 (2.66 to 6.51)1.74 (1.33 to 2.28)1.14 (0.92 to 1.42)Ref1.02 (0.74 to 1.42)0.99 (0.49 to 2.01)3.90 (1.23 to 12.32)<0.001
  • Reference group for comparison is 4.5–4.9 mEq/L. P value interaction between eGFR category and K=0.72. K+, potassium; 95% CI, 95% confidence interval; IRR, incidence rate ratio; Ref, reference.

  • a No adjustments were taken for crude rate calculations, which are expressed as events per patient-year. A Poisson distribution was used to construct the 95% CI of the crude rate for each eGFR stratum.

  • b IRRs were adjusted for prior hospitalization, age, sex, race/ethnicity, diabetes, congestive heart failure, coronary artery disease, cerebrovascular accident, and the use of four types of medications (loop diuretics, thiazide diuretics, renin-angiotensin-aldosterone system blockers, and nondihydropyridine calcium channel blockers). Poisson distributions were used.

  • c Model was not adjusted for race/ethnicity.

  • d Model was not adjusted for diabetes.