Sleep quality and blood pressure dipping in normal adults

Objectives: To investigate the relationship between sleep quality and nocturnal blood pressure dipping in normal subjects. We hypothesized that sleep quality correlates with dipping. Design: Cross-sectional study. Setting: Unattended polysomnography in the home followed by a 24-hour ambulatory blood pressure measurement. Patients: Eighty-eight self-described normal subjects were evaluated; 26 were excluded due to an apnea-hypopnea index greater than or equal to 10. None were taking antihypertensive medications. Interventions: N/A. Measurements and Results: Subjects were divided into dippers and nondippers based on greater than or equal to 10% drop in nocturnal mean arterial pressure (MAP). Sleep-quality variables included total sleep time; sleep latency; percentage of stages 1, 2, 3, 4, and rapid-eye- movement sleep; percentage of wake time after sleep onset (WASO); total arousal index; and sleep efficiency. Of the remaining 62 subjects, 17.7% were nondippers, and 7 were hypertensive. There was no difference in age, body mass index, apnea-hypopnea index, blood pressure, or sleep quality between groups. Stage 4 sleep correlated significantly with dipping of diastolic blood pressure and MAP (r = 0.410 and 0.378, respectively, P less than or equal to .002), and percentage of WASO was negatively correlated with dipping of diastolic blood pressure (r = -0.360, P =.004), suggesting that greater dipping was associated with better sleep quality. On multivariate analyses, Stage 4 sleep was independently associated with dipping of diastolic blood pressure (P = .034) after adjusting for screening MAP, percentage of WASO, total arousal index, and Stage 1 sleep. The same link was found between Stage 4 sleep and dipping of MAP (P = .05) after adjusting for screening MAP, age, sex, and body mass index. Repeat analyses excluding hypertensives yielded similar findings. Conclusion: Our data suggest that deeper and less-fragmented sleep is associated with more blood pressure dipping in normal subjects.