The circadian rhythms of blood pressure and heart rate in the hypertensive subjects: dippers and non-dippers.

The purpose of this study was to compare the circadian blood pressure and heart rate rhythm of dippers and non- dippers. Biochemical and clinical characteristics of dippers and non-dippers were also compared to determine whether non-dippers have an increased prevalence of hypertension- related conditions. The subjects were 123 out-patients with essential hypertension who had undergone ambulatory blood pressure monitoring at the University Hospital in Inchon, South Korea, from January 1, 1997 to December 31, 1998. Daytime values were determined between 6:00 AM and 8:00 PM and the nighttime values were determined between 8:00 PM and 6:00 AM. Non-dippers were defined as those who showed a reduction in systolic blood pressure, diastolic blood pressure or heart rate less than 10% and they accounted for 25%, 32% and 31% of the subjects, respectively. The timings of the circadian systolic and diastolic blood pressure and heart rate in dippers were very consistent: showing the lowest values during the night, rising in the early morning and reaching a plateau in the late morning. Non-dippers' circadian rhythms of systolic and diastolic blood pressures fluctuated less than those of dippers, and the 24-hours heart rate rhythms of the dipper and non- dipper groups were completely reversed. None of the biochemical characteristics tested in the present study showed a significant difference between dippers and non-dippers whether dipper was classified by systolic or diastolic blood pressure or heart rate. Similarly, hypertension-related symptoms and complications were not associated with the dipper/non-dipper description, whether classified by sBP, dBP, or HR.