Effect of Age and High Blood Pressure on Barorefiex Sensitivity in Man

TLDR

The study examined how baroreflex sensitivity varies with age and blood pressure in 81 untreated adults aged 19–66 with mean arterial pressures 70–150 mm Hg. Baroreflex sensitivity was quantified as the reflex increase in pulse interval (ms) per mm Hg rise in systolic pressure induced by phenylephrine injection. Baroreflex sensitivity ranged from 1.9 to 48.9 ms/mm Hg, showed no correlation with age or arterial pressure, and was independently diminished by increasing age and arterial pressure; subjects with a history of hypertension had lower sensitivity than age‑matched normotensives, while heart rate differences were minimal except in younger hypertensives.

Abstract

The purpose of this study was to relate baroreflex sensitivity to age and arterial pressure in 61 male and 20 female untreated subjects, aged 19-66 years, whose mean arterial pressures ranged from 70 to 150 mm Hg. In this selected group of subjects there was no correlation between age and arterial pressure. The index of sensitivity used was the increase in pulse interval which occurs reflexly in response to a rise in systolic pressure induced by the intravenous injection of phenylephrine and is measured as the increase in pulse interval in milliseconds per mm Hg rise in systolic blood pressure. It ranged from 1.9 to 48.9 msec/mm Hg. Increasing age and arterial pressure act independently to reduce baroreflex sensitivity. Eight subjects who had normal blood pressure at the time of testing but whose pressure had been elevated in the past, had reflex sensitivities significantly less than expected in persons of the same age and mean arterial pressure. The heart rate in these subjects was not significantly different from that in the controls; the heart rate of the 12 hypertensive subjects aged under 40 years was significantly faster than that of age-matched normotensive subjects but not that of older hypertensive subjects.