Aims: To determine whether the reduced nocturnal fall in blood pressure (BP) reported in elderly hypertensives is due to ageing or to the presence of hypertension.
Methods: Twenty-four hour ambulatory BP recordings of 68 normotensive elderly were compared with those of 55 elderly treated hypertensives, aged 63-88 years. Mean night-time BPs were calculated from the average of readings during sleep and mean daytime BPs from the remaining recordings. The maximum day-night BP differences were calculated. Plasma renin, aldosterone and noradrenaline were measured.
Results: Normotensive subjects were aged 72.0 +/- 4.7 years and treated hypertensives 73.7 +/- 4.9 years (p = 0.049). Normotensives had lower systolic BP (SBP) than hypertensives (125 +/- 12 mmHg versus 135 +/- 14 mmHg, p < 0.01). The fall in SPB at night was greater in normotensives than in hypertensives (18 +/- 9 versus 14 +/- 9 mmHg, p < 0.02). Non-dipping occurred in 24% of all subjects, with 59% of these being hypertensives. The nocturnal fall in SBP was not related to age (beta = -0.04, p < 0.62) but was inversely related to a history of hypertension (chi (2) = 5.82, p = 0.02). Serum noradrenaline was significantly related to nocturnal SBP fall (beta = 0.28, p = 0.01).
Conclusions: Elderly normotensives have a greater decline in nocturnal SBP than treated elderly hypertensives. The failure of SBP to fall at night appears to be more a feature of hypertension than of ageing. Early morning noradrenaline estimations are higher in patients with a greater nocturnal blood pressure fall.