Sodium Restriction Shifts Circadian Rhythm of Blood Pressure From Nondipper to Dipper in Essential Hypertension

<jats:p> <jats:italic>Background</jats:italic> Sodium restriction has been widely used for treatment of hypertension and renal diseases. Whether sodium restriction can transform the circadian rhythm of blood pressure from nondipper to dipper is examined. </jats:p> <jats:p> <jats:italic>Methods and Results</jats:italic> Patients (n=42) with essential hypertension were maintained on a high-sodium diet (12 to 15 g of NaCl per day) and a low-sodium diet (1 to 3 g/d) for 1 week each. On the last day of each diet, blood pressures were measured noninvasively every hour for 24 hours with an automatic oscillometric device. Twenty-one patients were classified as non–sodium sensitive whereas 21 were classified as sodium sensitive on the basis of a ≥10% change in 24-hour mean arterial pressure caused by sodium restriction. Nocturnal blood pressure fall was significant in the non–sodium sensitive subjects but not in sodium-sensitive subjects. There was a significant interaction between sodium restriction and nocturnal fall in blood pressure only in the sodium-sensitive subjects, indicating that the degree of the nocturnal fall was affected by sodium restriction. Furthermore, changes in the nocturnal fall induced by sodium restriction had a positive relationship with sodium sensitivity ( <jats:italic>r</jats:italic> =.38, <jats:italic>P</jats:italic> <.02) and a negative relationship with the nocturnal fall before sodium restriction ( <jats:italic>r</jats:italic> =−.75, <jats:italic>P</jats:italic> <.0001). </jats:p> <jats:p> <jats:italic>Conclusions</jats:italic> These findings show the difference in nocturnal fall in blood pressure between the non–sodium sensitive and sodium-sensitive types of essential hypertension. The diminished nocturnal fall, recognized in the sodium-sensitive type, is restored by sodium restriction, indicating that the circadian rhythm of blood pressure shifted from a nondipper to a dipper pattern. On the other hand, the nocturnal fall is not affected by sodium restriction in the non–sodium sensitive type, and the circadian rhythm remains of the dipper variety. </jats:p>