The optimal night-time home blood pressure monitoring schedule: agreement with ambulatory blood pressure and association with organ damage

Objective: Night-time home blood pressure (HBP) monitoring has emerged as a feasible, reliable and low-cost alternative to ambulatory blood pressure (ABP) monitoring. This study evaluated the optimal schedule of night-time HBP monitoring in terms of agreement with night-time ABP and association with preclinical target-organ damage. Methods: Untreated hypertensive adults were evaluated with ABP (24-h) and HBP monitoring (daytime: six days, duplicate morning and evening measurements; night-time: three nights, three-hourly automated measurements/night), and determination of left ventricular mass index, common carotid intima-media thickness and urinary albumin excretion. Results: A total of 94 patients with all nine night-time HBP measurements were analysed [mean age 51.8 +/- 11.1 (SD) years, men 57%). By averaging an increasing number of night-time systolic HBP readings, there was a consistent trend towards stronger association of night-time HBP with night-time ABP (correlation coefficients r increased from 0.69 to 0.81), and with target-organ damage indices (for left ventricular mass index r increased from 0.13 to 0.22, carotid intima-media thickness 0.12-0.25, urinary albumin excretion 0.33-0.41). However, no further improvement in the association was observed by averaging more than four to six night-time readings. The diagnostic agreement between HBP and ABP in detecting nondippers was improved by averaging more readings, with a plateau at four readings (single reading: agreement 81%, kappa 0.37; four readings: 88%, 0.49; nine readings: 84%, 0.40). Conclusion: A two-night HBP schedule (six readings) appears to be the minimum requirement for a reliable assessment of night-time HBP, which gives reasonable agreement with ABP and association with preclinical organ damage.