Why the study?
Do different methods of defining the night-time period (wrist actigraphy, cusum, fixed time) alter the assessment of nocturnal blood pressure and diurnal change in hypertensive and normotensive subjects?
Do different methods of defining the night-time period (wrist actigraphy, cusum, fixed time) alter the assessment of nocturnal blood pressure and diurnal change in hypertensive and normotensive subjects?
Routine use of wrist actigraphy does not significantly alter night-time BP values compared to a restrictive fixed-time definition (00.00-05.59), though dipping status classification varies by method.
Night-time BP values vary by definition; leaves open optimal standardization for ambulatory monitoring and dipping classification in research.
AIMS: To assess whether differences exist in nocturnal blood pressure (BP) levels and the diurnal BP change when using fixed time and wrist actigraphy methods to define the night-time period. METHODS: Untreated hypertensive (n = 48) and normotensive (n = 33) subjects (mean age 67 years: range 29-90) underwent simultaneous 24-h ambulatory BP monitoring and wrist actigraph monitoring. The diurnal BP change and nocturnal BP levels were assessed using two fixed night-time definitions-a reference period of 22.00-06.59 and also 00.00-05.59, as well as unedited and edited actigraph values and cumulative sums (cusums) analysis. RESULTS: The reference definition of night-time 22.00-06.59 resulted in the highest values for night-time BP compared to other definitions (p < 0.05), although actigraph defined night-time BP values were not significantly different from the more restrictive definition of night-time (00.00-05.59). Restrictive night-time, edited and unedited actigraph and cusums values for the day-night difference were all significantly greater than the value calculated using the reference night-time period. Dipping status changed significantly depending on which definition of night-time was used. CONCLUSIONS: Significant differences exist in nocturnal BP levels and circadian change between the various methods for defining night-time. The routine use of wrist actigraphy does not however appear to alter the value of night-time BP levels when compared to a more restrictive fixed-time definition of night-time.
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Youde et al. (1996) studied this question.