This study investigated the changes in circadian rhythms of plasma renin activity (PRA) and plasma aldosterone (PA) which occur in essential mesor-hypertensive women, increasing in age. Systemic blood samples were taken throughout a 12 h period from both mesor-hypertensive women and clinically healthy women (control). The women in each group were either post-menopausal or had normal menstrual cycles. A cosinor method of temporal series was the analysis employed to compute the properties of PRA and PA circadian rhythms. The clearest effect of ageing, recorded in essential mesor-hypertensive women, is a decrease in circadian mesor of PRA cycle (P = 0.002). The age-related changes in clinically healthy women appear to be more extensive and involve a decrease for both mesor (P < 0.001) and amplitude (P = 0.007) of PRA circadian rhythm. These disparities are convincing evidence for a non-physiological decline of the RAAS rhythmic function in the aged essential mesor-hypertensive women. The lack of an age-associated decrease in circadian PRA amplitude merits a pathophysiological and clinical investigation because it is a possible risk factor for post-menopausal, essential mesor-hypertensive women.
- Circadian rhythm