title: Comparison of diurnal systolic blood pressure change as defined by wrist actigraphy, fixed time periods and cusum.
abstract: OBJECTIVE
  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.
authors.affiliation: Department of Medicine, Glenfield Hospital, Leicester, UK.
authors.forename: J H
authors.initials: JH
authors.lastname: Youde
authors.forename: T G
authors.initials: TG
authors.lastname: Robinson
authors.forename: M A
authors.initials: MA
authors.lastname: James
authors.forename: S
authors.initials: S
authors.lastname: Ward-Close
authors.forename: J F
authors.initials: JF
authors.lastname: Potter
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001794:Blood Pressure / Q000502:physiology*; D018660:Blood Pressure Monitoring, Ambulatory; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged