Reactivity of ambulatory blood pressure to physical activity varies with time of day

Helen Jones, Greg Atkinson, Andrew Leary, Keith George, Michael Murphy, Jim Waterhouse

Research output: Contribution to journalArticleResearchpeer-review

60 Citations (Scopus)

Abstract

Blood pressure (BP) fluctuates over a 24-hour period, but it is unclear to what extent this variation is governed completely by changes in physical activity. Our aim was to use a BP "reactivity index" to investigate whether the BP response to a given level of physical activity changes during a normal sleep-wake cycle. Hypertensive patients (n=440) underwent simultaneous 24-hour ambulatory BP, heart rate (HR), and activity monitoring. BP and HR were measured every 20 minutes. Actigraphy data were averaged over the 15 minutes that preceded a BP measurement. Individual BP and HR reactivity indices were calculated using least-squares regression for twelve 2-hour periods. These indices were then analyzed for time-of-day differences using a general linear model. Systolic BP and HR were generally more reactive to physical activity than diastolic BP. The highest reactivity of systolic BP (mean± SE=4±1 mm Hg per logged unit change in activity) was observed between 8:00 AM and 10:00 AM (P=0.014). Between 10:00 AM and 12:00 PM, BP reactivity then decreased (P=0.048) and showed a secondary rise in the early afternoon. These 24-hour changes in BP reactivity did not differ significantly between groups formed on the basis of early and late wake times (P=0.485), medication use, age, and sex (P>0.350). In conclusion, under conditions of normal living, the reactivity of BP and HR to a given unit change in activity is highest in the morning and shows a secondary rise in the afternoon.

Original languageEnglish
Pages (from-to)778-784
Number of pages7
JournalHypertension
Volume47
Issue number4
DOIs
Publication statusPublished - 1 Apr 2006

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Exercise
Blood Pressure
Heart Rate
Actigraphy
Social Conditions
Least-Squares Analysis
Linear Models
Sleep

Cite this

Jones, Helen ; Atkinson, Greg ; Leary, Andrew ; George, Keith ; Murphy, Michael ; Waterhouse, Jim. / Reactivity of ambulatory blood pressure to physical activity varies with time of day. In: Hypertension. 2006 ; Vol. 47, No. 4. pp. 778-784.
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Reactivity of ambulatory blood pressure to physical activity varies with time of day. / Jones, Helen; Atkinson, Greg; Leary, Andrew; George, Keith; Murphy, Michael; Waterhouse, Jim.

In: Hypertension, Vol. 47, No. 4, 01.04.2006, p. 778-784.

Research output: Contribution to journalArticleResearchpeer-review

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