Pulse Rate and Sodium Intake Interact to Determine Blood Pressure: A Population Study

It has been suggested that certain factors need to be present for the pressor effect of sodium to become apparent. The present population study investigated whether pulse rate (PR) and salt intake interact to determine blood pressure (BP). Twenty-four hour urinary sodium (UNaV) was used as a measure of salt intake. A random population sample, including 2081 subjects with a minimum age of 18 years, was stratified on tertiles of PR. In subjects with a slow PR(less than 68 beats/min) and in those with a fast PR (greater than 78 beats/min), a significant curvilinear relationship between BP and UNaV was found, while in subjects with an intermediate PR the BP-UNaV correlation was not significant. There was also a significant interaction between PR and UNaV, indicating that when UNaV increased from 160 to 300 mmol/24 h, systolic/diastolic BP rose by 2/1 mm Hg in the fast PR third, but declined by 1/1 mm Hg in the slow PR third. These divergent trends could not be explained by smoking habits or alcohol consumption and were still present after cumulative adjustment for other important correlates of BP, ie, gender, age, body weight, urinary potassium, and contraceptive pill intake in women. In conclusion, the present data suggest that in subjects with a pulse rate greater than 78 beats/min a high salt intake may be associated with blood pressure elevation, whereas the opposite tendency is observed in individuals with a pulse rate less than 68 beats/min.