title: Time of day to monitor ambulatory blood pressure affects the outcome.
abstract: OBJECTIVE
  The reproducibility of blood pressure variables from ambulatory blood pressure monitoring (AMBP) initiated at the same time of day (SAME: 1700-1900 h) was compared with the reproducibility of blood pressure variables when monitoring was initiated at opposite times of day (OPP: randomized, morning=0700-0900 h and evening=1700-1900 h). It was hypothesized that the reproducibility for SAME (n=18) would be no different than the reproducibility for OPP (n=13).
  
  
  METHODS
  The order of AMBP sessions was randomized. The Accutracker II was used to determine average blood pressures, Crest (CrBP), Trough (TrBP), and TrBP : CrBP ratio; Averages were divided into 24-h, daytime (0600-2200 h), and night-time (2200-0600 h) for both systolic and diastolic blood pressures. A paired t-test with an intraclass correlation was used to determine the reproducibility of AMBP for both SAME and OPP. A chi-square was used to compare the distribution of reproducible AMBP variables between SAME and OPP. Significance was at P<0.05.
  
  
  RESULTS
  The reproducibility of AMBP variables for SAME and OPP was a significantly different for systolic blood pressure. All of the ambulatory systolic variables measured in the SAME group were reproducible except for the TrBP : CrBP, whereas only the systolic night-time averages of the OPP group were reproducible. Similarly all of the ambulatory diastolic variables measured in the SAME group were reproducible except for TrBP : CrBP, whereas 24-h, night-time averages, and TrBP were reproducible in the OPP group.
  
  
  CONCLUSIONS
  Ambulatory blood pressure variables were consistently higher when the monitoring session began in the morning hours.
authors.affiliation: Clinical Exercise Physiology Laboratory, Department of Kinesiology, Indiana University, Bloomington, Indiana 47405, USA. wallacej@indiana.edu
authors.forename: Janet P
authors.initials: JP
authors.lastname: Wallace
authors.forename: Saejong
authors.initials: S
authors.lastname: Park
authors.forename: Donald W
authors.initials: DW
authors.lastname: Zakutansky
authors.forename: Larissa A A
authors.initials: LA
authors.lastname: Lehmkuhl
authors.forename: Chester A
authors.initials: CA
authors.lastname: Jastremski
mesh_terms: D001794:Blood Pressure; D018660:Blood Pressure Monitoring, Ambulatory / Q000379:methods*; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D006973:Hypertension / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D013995:Time