Abstract MP09: Population Level 24-Hour Urinary Sodium and Potassium Associations With Blood Pressure Differs by Sex: Findings From the New York City Heart Follow-Up Study 2010 and 2018
Authors: Dasgupta Shabitri , Bholanath Tashema , Dongchung Tenzin Yangchen , Immerwahr Stephen , Lim Sungwoo , Browne Charmaine , Iftikhar Pulwasha , Dominianni Christine 
Published: May 2024

Introduction:
Hypertension (HTN) is a leading cause of heart disease and stroke amongst New York City (NYC) residents, with notable sex-based disparities in prevalence and cardiovascular (CV) outcomes. While prior 24-hour urinary population-based studies in other populations have shown that the association between sodium and potassium and blood pressure (BP) is primarily driven by hypertensive adults, the studies did not adequately evaluate how these associations may differ by sex.

Hypothesis:
Our study examined whether the relationship between sodium, potassium, and the sodium/potassium ratio and BP varies significantly by sex assigned at birth, stratified by HTN status, in the NYC population.

Methods:
The Heart Follow-Up Study (HFUS) is a cross-sectional survey conducted in 2010 and 2018 among NYC residents ages 18 and older. Study data included BP measurements, sodium and potassium urinary analytes, and self-reported information about CV health. Analyses were based on 1,606 and 2,327 participants, respectively, and weighted to the NYC population. HTN was defined as per the National Health and Nutrition Survey criteria: systolic BP≥140, diastolic BP≥90, or current use of HTN medication. We applied
t
-tests to detect differences in mean age-adjusted electrolyte excretions between hypertensive and normotensive adults, stratified by sex. Furthermore, we used multivariable linear regression models, which included sex as an interaction term, to assess the association between sodium and potassium intake and BP at the two time points, and to evaluate potential effect modifications by sex.

Results:
In 2018, we observed no substantial difference between the mean age-adjusted 24-hour urinary excretion of sodium, potassium, and sodium/potassium ratio and HTN status among NYC males or females (
p
>.05). From multivariable models, we observed a consistent positive association between sodium/potassium ratio and mean BP in normotensive males; the relationship was stronger in 2010 (2.060, 95% CI: 0.865-3.255) compared to 2018 (0.312, 95% CI: 0.101-0.523). However, this association was not evident in normotensive females at both time points. We did not observe a consistent association between sodium, potassium, and sodium/potassium ratio and BP within the HTN group in males or females at either time point.

Conclusions:
The association between sodium/potassium levels and BP differs by sex. This association was evident exclusively in normotensive males, although we noted that the magnitude of this association was smaller in 2018 than in 2010. This suggests that sodium/potassium excrement may be a stronger indicator for BP variations within this subgroup. Recognizing that sex-based variations exist, our results suggest conducting intra-sex analysis to better understand CV health disparities and develop tailored public health strategies that will reduce adverse CV outcomes.