Reproducibility of nocturnal blood pressure assessed by self-measurement of blood pressure at home

To assess the reproducibility of nocturnal blood pressure (BP) during sleep as measured using a self-measurement device at home, we obtained repeated nocturnal home BP at 0200 h and quality of sleep assessment from a diary in 556 subjects (71% women, 62.4±11.1 years) in the general population. We used an Omron device (HEM-747IC-N, Omron Healthcare Co., Ltd., Kyoto, Japan), with which the time and frequency of monitoring can be preset and the readings stored. The mean±SD of the difference between test-retest BP measurements was 0.7±15.1 mmHg systolic and 0.2±9.7 mmHg diastolic with a mean interval of 5.9 days. The absolute differences were greater than 10 mmHg in 261 (46.9%) subjects for systolic and 145 (26.0%) subjects for diastolic. There was no evidence of regression to the mean in nocturnal measurements over at least three nights (n=390, p>0.22). The differences (the first minus the second measurement) were large in subjects who experienced sleep disturbance only in the first (n=64, 2.3±13.6 mmHg and 1.6±9.6 mmHg for systolic and diastolic, respectively) or second sessions (n=56, -4.1±16.4 mmHg and -2.5±11.4 mmHg) compared with the subjects without sleep disturbance (n=66, 1.5±17.8 mmHg and 0.8±10.3 mmHg) and those with sleep disturbance (n=370, 0.9±14.5 mmHg and 0.2±9.3 mmHg) in both sessions. In conclusion, the reproducibility of single nocturnal BP as assessed using a self-measurement device at home was not good, especially for subjects who experienced different quality of sleep in each session. To evaluate nocturnal BP using a self-measurement device, estimation of quality of sleep is indispensable.