Blood pressure variability and reactivity in the natural environment

Abstract

Laboratory studies have found that individuals with mild hypertension differ from normotensives in their degree of blood pressure variability and reactivity, defined as the change in blood pressure to specific stimuli. Based on the assumption that mild hypertension represents an intermediate stage in the development of established hypertension, these studies have led to the speculation that exaggerated blood pressure variability and/or reactivity plays an etiological role in the development of established hypertension [1–3]. These findings, however, have not been extended to blood pressure functioning under natural, day-to-day conditions. In the present study we examined blood pressure variability and reactivity over a 24-h period in three groups of individuals: a) normotensive control subjects, defined as a clinic blood pressure ≧ 120/80 mm Hg, b) mild hypertensive subjects, defined as a clinic blood pressure > 120/80 mm Hg < 160/104 mm Hg; and c) established hypertensive subjects, defined as a clinic blood pressure > 160/104 mm Hg. There are no generally accepted ways of measuring blood pressure variability and reactivity in the natural environment [4]; therefore, in this study we have chosen to define variability in three different ways: a) the blood pressure pattern based upon the location/activity in which the measurement was obtained; b) the overall variability of blood pressure; and c) the range in blood pressure. Reactivity was defined as a) blood pressure responses obtained during the performance of activities with either physical or b) psychological demands relative to blood pressure during relaxation, as well as c) the percentage of readings less than the individual’s own clinic reading.