Different Seasonal Variations of Potassium in Hemodialysis Patients with High Longitudinal Potassium Levels: A Multicenter Cohort Study Using DialysisNet

Abstract

Purpose: To determine seasonal variations in serum potassium levels among hemodialysis patients.

Materials and methods: This was a multicenter cohort study of patients whounderwent hemodialysis and were registered in DialysisNet at our four associated general hospitals between January and December 2016. Month-to-month potassium variability was quantified as SD/√{n/(n-1)}, and a non-hierarchical method was used to cluster groups according to potassium trajectories. Seasonal variations in potassium levels were analyzed using a cosinor analysis.

Results: The analysis was performed on 279 patients with a mean potassium level of 5.08±0.58 mmol/L. After clustering, 52.3% (n=146) of patients were included in the moderate group (K⁺, 4.6±0.4 mmol/L) and 47.7% (n=133) in the high group (K⁺, 5.6±0.4 mmol/L). The mean potassium level peaked in January in the moderate group (4.83±0.74 mmol/L) and in August in the high group (5.51±0.70 mmol/L). In the high potassium group, potassium levels were significantly higher in summer than in autumn (p<0.001) and spring (p=0.007). Month-to-month potassium variability was greater in the high group than in the moderate group (0.59±0.19 mmol/L vs. 0.52±0.21 mmol/L, respectively, p=0.012). Compared to patients in the first quartile of potassium variability (≤0.395 mmol/L), those with higher variability (2nd-4th quartiles) were 2.8-4.2 fold more likely to be in the high potassium group.

Conclusion: Different seasonal patterns of serum potassium were identified in the moderate and high potassium groups, with potassium levels being significantly higher in the summer season in the high potassium group and in winter for the moderate potassium group.

Keywords: End-stage renal disease; hemodialysis; potassium; seasonal variation.

Fig. 1. Group clustering according to serum potassium trajectories. (A) Comparison of internal validation of clustering analysis by concordant criteria. The line numbers 1, 2, 3 are Calinski Harabatz index, 4 is RayTuni index, and 5 is Davies Bouldin index. Concordant criteria showed agreement on two group clustering (red circle). (B) The difference in potassium levels between groups along with the seasons.

Fig. 2. Cosinor analysis for the variation of serum potassium level. The seasonal pattern at which the peak of a rhythm occurred (acrophase) was from June to August in the high potassium group, whereas the acrophase occurred from September to December in the moderate potassium group.

Fig. 3. Comparison of seasonal potassium levels by group. (A) Moderate group. (B) High group.

Fig. 4. Survival analysis for the longitudinal potassium level. (A) Kaplan-Meier analysis for survival according to K⁺ clustering group. (B) Kaplan-Meier analysis for survival according to K⁺ variability.