To investigate the relationships among diurnal blood pressure (BP) variations and autonomic nervous system dysfunction, we assessed heart rate variability (HRV) using power spectral analysis of the 24-hour RR interval in 51 asymptomatic elderly hypertensive patients with various patterns of nocturnal BP fall. The extreme-dippers with marked nocturnal BP fall (n=16) had lower asleep low-frequency power (LF)/high-frequency power (HF) ratios (a relative index of sympathetic nervous system activity), while the nondippers without nocturnal BP fall (n=18) had lower awake LF/HF ratios and asleep/awake ratio for HF (an index of parasympathetic nervous activity), when compared with dippers with appropriate nocturnal BP fall (n=17). The incidence of multiple lacunar infarction detected by brain magnetic resonance imaging was 56% in the extreme-dippers and 38% in the nondippers, and both were markedly higher than that (6.3%) in the dippers (both P<.01). There was no significant relationship between the BP level and any HRV parameter for either the daytime or nighttime period. The asleep/awake ratio for systolic BP was significantly correlated with the asleep/awake ratio for HF (r= -.363, P<.01) and with the asleep/awake ratio for the LF/HF ratio (r=.540, P<.001), regardless of whether multiple lacunar infarction was present. In conclusion, the autonomic nervous system activity is not related to high BP level per se, rather its diurnal variation is more important as a determinant of the diurnal BP patterns, regardless of the presence or absence of cerebrovascular disease.

Abstract-Among elderly hypertensive subjects, extreme dippers with marked nocturnal fall in blood pressure (BP) as well as nondippers with absent nocturnal fall in BP are more prone to cerebrovascular disease when compared with those with appropriate nocturnal BP fall. However, the relationship between these abnormal diurnal BP variation patterns and postural BP variation has not been investigated. We investigated the diurnal BP variation by ambulatory BP monitoring and postural BP variation during 70°head-up tilt in 110 asymptomatic hypertensive elderly subjects, who consisted of 29 subjects with white-coat hypertension and 81 with sustained hypertension with various patterns of nocturnal fall in BP (14 extreme dippers, with asleep systolic BP decrease by Ն20% of awake systolic BP; 56 dippers, with decrease by Ն0% to Ͻ20%; 11 nondippers, with decrease by Ͻ0%). During tilt, the mean (SD) systolic BP increased 10 (19) mm Hg in the extreme dippers (PϽ.02), and it decreased by 7.5 (13) mm Hg in the nondippers (PϽ.05), whereas it did not change in the dippers and white-coat hypertensive subjects. The heart rate increased in all four groups to similar degrees during tilt. Orthostatic hypertension defined as systolic BP rise of 10 mm Hg or more during tilt was found in 10 (72%) of the 14 extreme dippers, 6 (11%) of the 56 dippers, and 1 (9%) of the 11 nondippers, while orthostatic hypotension defined as systolic BP decrease of 20 mm Hg or more was found in 3 (27%), 5 (9%), and 1 (7%) of the nondippers, dippers, and extreme dippers, respectively ( 2 ϭ29.3, PϽ.0001). In conclusion, the abnormal diurnal BP variation is closely related to the abnormal postural BP variation in elderly hypertensive patients, with extreme dippers showing orthostatic hypertension and nondippers showing orthostatic hypotension. The upright position during the daytime, which increases the BP in the extreme dippers and decreases it in the nondippers, may in part produce abnormal diurnal BP variation. A n abnormal pattern of diurnal BP variation has been reported to carry a high risk for cardiovascular disease in hypertensive patients. Nondippers, with diminished nocturnal BP fall, have been proposed as one subgroup with abnormal diurnal BP variation characterized as associated with increased frequency of damage to all target organs (brain, heart, and kidney) and poorer prognosis for cardiovascular events, when compared with dippers with appropriate nocturnal BP fall. [1][2][3][4] In addition to nondippers, recently we identified among dippers the subgroup of extreme dippers, with marked nocturnal BP fall, as having a newly recognized subtype of abnormal diurnal BP variation, and we found that among elderly hypertensive patients extreme dippers have more marked cerebrovascular damage than do dippers. 5The extreme pattern of diurnal BP variations in extreme dippers or extreme nondippers (whose sleep BP is actually higher than their awake BP) is a relatively persistent trait. 6 However, the mechanism of these abnormal BP variation patterns in hyper...