Sleep structure in essential hypertensive patients: differences between dippers and non-dippers

The objective of this study was to determine whether the macrostructure and microstructure of sleep were altered in non-dipper essential hypertensive patients. Patients included 9 non-dipper essential hypertensive patients and 10 dippers. We measured blood pressure beat-to-beat by Finapres and all stages of sleep by polysomnografically recording simultaneously during spontaneous nocturnal sleep. We analysed blood pressure pattern for 4-min long random periods while the patients were awake and during all stages of sleep; sleep-efficiency (SE), sleep-latency (SL), delta sleep-latency (delta-SL), REM sleep-latency (REM-SL), St. 1, St.2, St.3, St.4 and REM duration and percentage (%) values, and microstructural aspects of sleep (arousal and microarousal temporisation and features). Dipper patients showed a fall in blood pressure (BP) greater than 10% in all stages of NREM sleep; in the non-dipper patients BP fell by less than 10% of waking values in all NREM stages. REM sleep as well as HR were similar in both groups during all stages of sleep. Non-dippers showed the same number of arousals but more microarousals than dippers (p < 0.001). During and after microarousals BP and HR increased in non-dippers, but showed light variation in dippers. Microarousals induced several stage shifts towards lighter sleep. For this reason non-dippers spent less time in stage 4 than dippers (p < 0.001). In conclusion, non-dipper essential hypertensive patients are a subset of patients with central sympathetic hyperactivity responsible for quantitative and qualitative alteration of sleep.