The lack of nocturnal decline in lood pressure (BP) has been associated with an increase in end-organ-damage and cardiovascular events [Verdecchia et al. Hypertension 1994;24:793-801], although results are still controversial partly due to the inability to properly reproduce over time the classification of patients into dippers and non-dippers [Omboni et al. J Hypertens 1988;16:733-738]. Moreover, the non-dipping status has been frequently related to an increase in nocturnal activity and/or differences in quality of sleep [Kario et al. Hypertension 1999;34:685-691]. With the aim to assess the relationship between activity and BP, we studied 160 mild-to-moderate hypertensive patients (82 men), 54.2±1.3 (mean±SE) years of age. BP was measured at 20-minute intervals during the day and at 30-minute intervals at night for 48 consecutive hours with an ambulatory Spacelabs 90207 device. Physical activity was simultaneously monitored by wrist actigraphy. Circadian parameters of BP and activity established by population multiple-components analysis [Fernández & Hermida. Chronobiol Int 1998;15:191-204] were compared between dippers (n=67) and non-dippers (systolic nocturnal decline<10%) by nonparametric testing. Diurnal and nocturnal means of BP and activity were computed for each patient according to individual resting hours determined by actigraphy. Despite highly statistically significant differences in nocturnal mean as well as in each hourly nightly mean of BP between dippers and non-dippers, there were no differences on those parameters in activity. Duration of sleep as well as 24-hour mean and standard deviation of activity were also similar between groups (P>0.108), although non-dippers have a slightly decrease in diurnal mean of activity (P=0.030). The highly significantly different circadian variation in BP between dipper and non-dipper patients with essential hypertensive is not related to a significant increase in nocturnal physical activity.
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