The relationship between estimated salt intake and central systolic blood pressure in Japanese outpatients with hypertension

Background: Recent reports suggest that central blood pressure (BP) may be instrumental in the diagnosis and management of hypertension. Several reports have shown an association between salt intake and central hemodynamics, especially central systolic BP; however, this relationship remains unclear in Japanese outpatients with hypertension. Therefore, this study investigated the relationship between central systolic BP and salt intake in Japanese outpatients with hypertension. Methods: We recruited 141 Japanese outpatients with hypertension. Their daily salt intake was estimated using spot urine samples. Their central systolic BP was measured using an Omron HEM-9000AI device. Results: The median estimated salt intake was 9.81 (range, 8.34-11.47) g/day. The mean brachial systolic/diastolic BP and central systolic BP were 131.2 ± 16.5 /78.1 ± 10.9 mmHg and 135.6 ± 17.3 mmHg, respectively. The estimated salt intake was divided into four quartiles, with central systolic BP significantly higher in Q3 and Q4 than that in Q1 (P < 0.01). A significant positive correlation was observed between central systolic BP and estimated salt intake (r=0.275, P=0.001). Multiple regression analysis of central systolic BP showed that the estimated salt intake and BMI were significant factors (P = 0.014 and P = 0.027, respectively). Conclusions: We found that our Japanese outpatients with hypertension consumed higher amounts of salt than the target value recommended by Japanese guidelines. In addition, there was a moderate relationship between central systolic BP and the estimated salt intake. Therefore, a decrease in salt intake is important, even in outpatients with hypertension receiving antihypertensive medication.