The association of blood pressure with estimated urinary sodium, potassium excretion and their ratio in hypertensive, normotensive, and hypotensive Chinese adults.

Background and Objectives: Low sodium and high potassium intake is reported to be a risk of hypertension. However, it is uncertain whether these associations can be generalized to those without hypertension. This study is to evaluate the associations of systolic and diastolic blood pressure (SBP and DBP, respectively) with estimated urinary sodium excretion (eUNaE), estimated urinary potassium excretion (eUKE) and their ratio (Na/K ratio) among hypertensive, normotensive, and hypotensive Chinese individuals.
Methods and Study Design: A large institution-based cross-sectional study was conducted at the Third Xiangya Hospital, Changsha between August 2017 and November 2018. Spot urine samples were collected to test urinary sodium, potassium, and creatinine excretions for each participant. The Kawasaki formula was used to estimate 24-hour urinary sodium and potassium excretions.
Results: A total of 26,363 eligible subjects were used to analyze the associations of blood pressure with eUNaE, eUKE, and their ratio. 27.3% (n=7,201) of participants were diagnosed with hypertension, 5.4% (n=1,427) were diagnosed with hypotension, and the remaining of 17,735 participants were normotensive. A significant increase in SBP and DBP was related to the Na/K ratio increase in hypertensive and normotensive subgroups (all ptrend<0.01), but the association was not significant for DBP among hypotensive individuals (ptrend=0.58). Stronger associations of SBP with the Na/K ratio were observed in older people (pinteraction<0.01) and females (pinteraction<0.0001), but the same trend was not observed for DBP (pinteraction=0.10 and 0.88, respectively).
Conclusions: High potassium and low sodium intake were further confirmed to reduce blood pressure in hypotensive, normotensive, and hypertensive individuals.