Objective  To analyze the association of urinary sodium, urinary potassium, and the sodium-to-potassium ratio with blood pressure levels among seafarers.

Methods  Data from 715 seafarers undergoing physical examinations at the Physical Examination Center of Ningbo Rehabilitation Hospital, Zhejiang Province, from February 2025 to July 2025 were collected. Clinic supine blood pressure was measured using an automated arteriosclerosis detector on both arms, with the arm showing the higher systolic pressure selected as the reference arm. General information, as well as the concentrations of urinary sodium and urinary potassium from morning fasting spot urine samples, were collected, and the urinary sodium-to-potassium ratio was calculated. Pearson correlation analysis and multiple linear regression analysis were used to explore the association of morning fasting spot urinary sodium and potassium concentrations and the urinary sodium-to-potassium ratio with reference arm blood pressure levels.

Results  The mean age of the subjects was (43.66±12.70) years. The reference arm blood pressure was (130.29±14.44)/(85.52±11.21) mmHg, urinary sodium was (134.96±55.77) mmol/L, urinary potassium was (55.44±28.17) mmol/L, and the urinary sodium-to-potassium ratio was 3.05±1.94. Correlation analysis showed no statistically significant association between urinary sodium and reference arm blood pressure (P＞0.05). However, urinary potassium was negatively correlated with both systolic blood pressure (r = −0.133, P＜0.001) and diastolic blood pressure (r = −0.148, P＜0.001). The urinary sodium-to-potassium ratio was positively correlated with both systolic blood pressure (r = 0.134, P＜0.001) and diastolic blood pressure (r = 0.114, P=0.002). Multiple regression analysis results indicated that urinary potassium and the urinary sodium-to-potassium ratio were associated with both systolic and diastolic blood pressure (P＜0.001).

Conclusion Morning fasting spot urinary potassium and the urinary sodium-to-potassium ratio are correlated with reference arm blood pressure. Seafarers should be advised to increase potassium intake while restricting sodium salt intake.