The Effects of Physical Activity and Autonomic Nerve Tone on the Daily Fluctuation of Blood Pressure

The effects of daily activity and autonomic nerve tone on the fluctuation of ambulatory blood pressure were studied in hypertensive patients. The autonomic nerve tone was measured by frequency domain analysis of the RR interval. Physical activity was evaluated by a walk count, converted to a walk rate (WR), recorded using a digital Holter ECG fitted with an accelerometer, with simultaneous monitoring of blood pressure (Bp). Average values of the WR, H and L/H components were calculated for the 15 min. period just prior to Bp monitoring. The relationship between the average WR, H and L/H values and the Bp was determined by a linear regression analysis. Hypertension was classified into three types, autonomic nerve dominant (AN), exercise dominant (EX), and irregular (IR), based on a high correlation coefficient between Bp and either H or L/H (AN type), between Bp and WR (EX type), or no significant correlation between Bp and any of the parameters (IR type). Of the thirty hypertensive patients studied 11 were classified as AN, 12 as EX, and 7 as IR. Patients of the EX type had significantly lower Bp than patients in the other two classes. Furthermore, all of the IR type patients showed non-dipper type hypertension, suggesting that the Bp regulation mechanisms were impaired. The results suggest the significance of simultaneous monitoring of physical activity and autonomic nerve function at the time of Bp monitoring.