title: Reproducibility of blood pressure dipping: relation to day-to-day variability in sleep quality.
abstract: Previous studies of the reproducibility of blood pressure (BP) dipping have yielded inconsistent results. Few have examined factors that may influence day-to-day differences in dipping. Ambulatory BP monitoring was performed on three occasions, approximately 1 week apart, in 115 untreated adult subjects with elevated clinic BPs. The mean ± standard deviation BP dip was 18 ± 7/15 ± 5 mm Hg (sleep/awake BP ratio = 0.87 ± 0.05/0.82 ± 0.06), with a median (interquartile range) day-to-day variation of 5.2 (3.1-8.1)/4.3 (2.8-5.6) mm Hg. There was no decrease in variability with successive measurements. The reproducibility coefficient (5.6 [95% confidence interval, 5.1-6.1] mm Hg) was greater and the intraclass correlation coefficient (0.53 [95% confidence interval, 0.42-0.63]) was smaller for the systolic dip than for 24-hour or awake systolic BPs, suggesting greater day-to-day variability in dipping. Variability in systolic dipping was greater in subjects with higher awake BP, but was not related to age, gender, race, or body mass index. Within individuals, day-to-day variations in dipping were related to variations in the fragmentation index (P < .001), a measure of sleep quality. Although mean 24-hour and awake BPs were relatively stable over repeated monitoring days, our study confirms substantial variability in BP dipping. Day-to-day differences in dipping are related to sleep quality.
authors.affiliation: University of North Carolina at Chapel Hill, Chapel Hill, NC. Electronic address: hinderli@med.unc.edu.
authors.forename: Alan L
authors.initials: AL
authors.lastname: Hinderliter
authors.affiliation: Duke University Medical Center, Durham, NC; Nell Hodgson Woodruff School of Nursing, Emory University, Atlanta, GA.
authors.forename: Faye S
authors.initials: FS
authors.lastname: Routledge
authors.affiliation: Duke University Medical Center, Durham, NC.
authors.forename: James A
authors.initials: JA
authors.lastname: Blumenthal
authors.affiliation: University of North Carolina at Chapel Hill, Chapel Hill, NC.
authors.forename: Gary
authors.initials: G
authors.lastname: Koch
authors.affiliation: University of North Carolina at Chapel Hill, Chapel Hill, NC.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Hussey
authors.affiliation: Psychology Service, Miami VA Healthcare System, Miami, FL.
authors.forename: William K
authors.initials: WK
authors.lastname: Wohlgemuth
authors.affiliation: Duke University Medical Center, Durham, NC.
authors.forename: Andrew
authors.initials: A
authors.lastname: Sherwood
mesh_terms: D056044:Actigraphy; D000328:Adult; D001794:Blood Pressure / Q000502:physiology*; D018660:Blood Pressure Monitoring, Ambulatory / Q000379:methods* / Q000592:standards*; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D006973:Hypertension / Q000175:diagnosis / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012890:Sleep / Q000502:physiology*; D012892:Sleep Deprivation / Q000175:diagnosis / Q000503:physiopathology
keywords: Ambulatory blood pressure monitoring; actigraphy; fragmentation index