Trends in Urinary Sodium-to-Potassium Ratios in Koreans: Analysis of KNHANES 2016–2023 Data

<b>Background/Objectives</b>: Recent Japanese guidelines recommend using the average sodium-to-potassium (Na/K) ratio from casual urine samples to assess hypertension and cardiovascular risk, suggesting cutoffs of 2 (optimal) and 4 (feasible). We aimed to evaluate the proportion of Korean individuals who would be classified as having elevated Na/K ratios using these cutoffs, based on random urine Na/K measurements obtained from the nationally representative Korea National Health and Nutrition Examination Survey (KNHANES) dataset. <b>Methods</b>: We analyzed 50,440 participants from the KNHANES 2016-2023 with available random urine Na and K results. Annual urinary Na/K ratios were calculated, and the prevalence of ratios ≥2 and ≥4 was assessed by age and sex using sampling weights. <b>Results</b>: The weighted median Na/K ratios were consistently lower than the weighted means, indicating skewed distributions. From 2016 to 2023, the weighted median and mean values increased from 2.3 and 2.7 to 2.8 and 3.3, respectively. The prevalence of a Na/K ratio ≥2 increased from 60.5% to 72.0%, and that of a ratio ≥4 increased from 16.9% to 28.3%. A U-shaped trend in Na/K ≥4 prevalence was observed by age, highest among those <20 and ≥70 years. Males had a higher prevalence than females in all age groups except 20-29. <b>Conclusions</b>: A growing proportion of Koreans exceeded Na/K cutoffs of 2 and 4 over time. Age- and sex-specific variation suggests tailored interpretation may be necessary when applying these thresholds in population health monitoring.