LAUSR

Objectives: High sodium intake is strongly associated with hypertension and obesity. This study aims to investigate the relationship between 24-h urinary sodium (a surrogate measure of sodium intake), ambulatory blood pressure parameters, left atrial function, and left atrioventricular coupling. Further, we intend to examine whether blood pressure and BMI might be mediators of the relationship between 24-h urinary sodium and subclinical cardiac function. Methods: Our study had 398 participants, all of whom were subjected to 24-h urine collection, 24-h ambulatory blood pressure measurement, and cardiac magnetic resonance imaging. Results: The average age of the participants was 55.70 ± 11.30 years old. The mean urinary sodium of the participants was 172.01 ± 80.24 mmol/24 h. After adjusting for age, sex, history of diabetes, smoking status, alcohol consumption, and use of diuretics, 24-h urinary sodium was correlated with multiple ambulatory blood pressure parameters, BMI, left atrial function, and the left atrioventricular coupling index (LACI) (P < 0.05). Mediation analysis showed that BMI explained 16% of the indirect effect of 24-h urinary sodium and left atrial function and 30% of the indirect effect of LACI. Independent of the mediator, 24-h urinary sodium had a significant direct effect on left atrial function and left atrioventricular coupling. Conclusions: Higher 24-h urinary sodium was associated with a greater BMI as well as poor left atrial function and left atrioventricular coupling, and the BMI mediated the relationship between 24-h urinary sodium and subclinical left cardiac function. Furthermore, and more importantly, 24-h urinary sodium may have directly affected the left atrial function and left atrioventricular coupling independent of intermediary factors.