[Nocturnal drop of arterial blood pressure: determinant factors and relationship with organic damage secondary to hypertension].

OBJECTIVES

To evaluate the night-time drop in blood pressure in patients with light hypertension and to determine its possible relationship with damage in key organs.

DESIGN

Cross-sectional study.

SETTING

Eight urban health centres.

PATIENTS: Four hundred and eighteen adults with light-moderate hypertension.

INTERVENTIONS: a) Blood pressure reading on three visits; b) ambulatory monitoring of pressure for 24 hours; c) echocardiograph (in 219 patients); d) albuminuria determination (in 134 patients). A night-time drop in blood pressure was defined as the difference between day and night ambulatory pressures; and relative drop, as the night-time pressure drop as a percentage of the day-time pressure.

RESULTS

Night-time drop in systolic and diastolic pressures was 13.6 (10.7) and 12.1 (8.6) mmHg, respectively. The predictive factors of night-time drop in blood pressure were, directly, daily ambulatory blood pressure (p < 0.05) and female gender (p < 0.05) and, inversely, age (p < 0.05). No association was observed between night-time drop in blood pressure and left ventricular mass. Only in women was an independent relationship found, inversely, between night-time drop in blood pressure and urinary excretion of albumin (p < 0.05).

CONCLUSIONS

Relative night-time drop in blood pressure is greater in women than in men, diminishes with age and depends on the day-time ambulatory pressure. In women a minor night-time drop in blood pressure is associated with greater organic damage.