Background: Excess salt intake is one of the most important causes of hypertension and salt restriction by lifestyle modification results in a reduction of blood pressure. Salt restriction is recommended as a key strategy in the management of hypertension and, thus, should be instructed for hypertensive patients under medical treatment.
Purpose: We investigated recent changes in dietary salt intake and blood pressure (BP) levels in hypertensive patients under antihypertensive treatment.
Methods: Total of 12422 hypertensive subjects (male 8814, mean age 64.6±9.2 year-old) under antihypertensive medications who visited our hospital for a physical checkup between 2010 and 2016 were enrolled. They were divided into 3 groups according to the number of antihypertensive drugs prescribed (1, 2 and ≥3 drugs). Cross-sectional analyses were performed using data in each year during the period and changes during the 7 years were investigated. Individual salt intake was estimated using a spot urine by a previously reported method.
Results: BP levels and the accomplishment rate of the target BP (<140/90mmHg) were improved during the 7 years (132.7±13.6/80.0±8.9 to 128.8±13.7/76.3±9.6 mmHg, 65.6 to 76.4%; respectively) without a significant difference among the groups. In contrast, individual salt intake was gradually increased in all groups (11.7±3.7 to 12.2±4.0, 11.9±3.7 to 12.7±3.9, and 12.2±3.9 to 12.9±4.1 g/day in 1, 2, and ≥3 drugs groups, respectively). Over all, the accomplishment rate of the target salt intake (<6g/day) was decreased with increasing the number of antihypertensive drugs (3.5, 2.8, and 2.3% in the groups with 1, 2, and ≥3 drugs, respectively). The accomplishment rate of the target BP was significantly higher in patients who achieved the target salt intake than in those who did not in all groups (Over all; 80.2 vs. 73.3%).
Conclusions: The control of BP in individuals under antihypertensive medications has been improved during the last 7 years. However, dietary salt intake has not been reduced and salt restriction has not been successfully achieved especially in hypertensive patients with multiple antihypertensive medications. Excess salt intake may induce resistance to antihypertensive treatment and, thus, increase the number of antihypertensive drugs for BP control.