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Study Title and Description

Acute effects of caffeine on blood pressure and wave reflections in healthy subjects: should we consider monitoring central blood pressure?



Key Questions Addressed
1 For [population], is caffeine intake above [exposure dose], compared to intakes [exposure dose] or less, associated with adverse effects on cardiovascular outcomes?
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Primary Publication Information
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TitleData
Title Acute effects of caffeine on blood pressure and wave reflections in healthy subjects: should we consider monitoring central blood pressure?
Author E Karatzis,TG Papaioannou,K Aznaouridis,K Karatzi,K Stamatelopoulos,A Zampelas,C Papamichael,J Lekakis,M Mavrikakis,
Country
Year 2005
Numbers

Secondary Publication Information
There are currently no secondary publications defined for this study.


Extraction Form: Cardiovascular Design
Design Details
Question... Follow Up Answer Follow-up Answer
What outcome is being evaluated in this paper? Cardiovascular
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What is the objective of the study (as reported by the authors)? The present study sought to examine the acute effect of caffeine (in the common used quantity of one cup of coffee) on both peripheral and central blood pressure, as well as on indices of wave reflections and pulse wave velocity (PWV), in normal young volunteers.
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Provide a general description of the methods as reported by the authors. Information should be extracted based on relevance to the SR (i.e., caffeine related methods) Subjects Sixteen healthy volunteers (eight females and eight males, mean age 29 +/- 3.2 years, range 24–38 years) were recruited in the study. All subjects were normotensives, not obese and did not suffer from diabetes mellitus, kidney, liver or other metabolic disorders. Caffeine abstainers, smokers, women using contraceptives and chronic users of any vasoactive medication were excluded from the study. Design A randomized, double-blind, crossover design was followed. Subjects were asked to consume a cup of warm instant coffee containing 80 mg caffeine, or a cup of warm decaffeinated coffee within 10 min, on 2 different days, 1 week apart. The study was conducted early in the morning in a room maintained at a constant temperature 21–23oC, while a resting period of 30 min was allowed for every volunteer before the beginning of each session of the study. Subjects were examined in the supine position at fast and 30, 60, 90 and 120 min following the ingestion of each beverage. All volunteers were instructed to abstain from products containing caffeine (such as tea, chocolate, soft caffeinated drinks, etc.), ethanol and food for at least 12 h before the study. Hemodynamic measurements Peripheral blood pressures were measured at the brachial artery via the detection of Korotkoff sounds using a sphygmomanometer placed around the nondominant upper arm. Three measurements were obtained and the mean value of systolic (SBP) and diastolic pressure (DBP) was calculated and used in the analysis. Central blood pressures were estimated noninvasively by using a fully automated and validated system (AtCor Medical, Sydney, Australia). The method applied for the estimation of aortic pressure waveforms is based on the recording of the peripheral pressure waves via applanation tonometry of the radial artery and their transformation to the respective aortic waveforms by using generalized transfer functions. Augmentation index % (AI%= 100 x AP/pulse pressure) represents the pressure boost (AP: augmentation pressure) that is induced by the return of the reflected waves at aorta as a percentage of pulse pressure. The augmentation of systolic pressure due to wave reflections results to an additional ‘‘pulsatile’’ load which must be overcome by the left ventricle during systole. Higher values of AI are associated with increased wave reflections which are mainly accompanied by an increase in pulse wave velocity, arterial stiffness and peripheral resistance. Arrival time (delta-t, ms) of reflected waves at aorta represents the time needed for pressure waves to travel from the aorta to peripheral arterial sites and return back to the aorta due to wave reflections. Travel time of pressure waves is determined directly by the velocity of pressure waves and indirectly by (i) the arterial stiffness, (ii) the period of the cardiac cycle and (iii) the distance between left ventricle and the peripheral reflecting sites of the arterial system. Lower values of delta-t indicate short travel time of the pressure waves, and increased pulse wave velocity and higher arterial stiffness. Statistical Analysis Analysis of variance (ANOVA) for repeated measures was used to evaluate the changes over time in variables measured at both trials (coffee and control). A further ANOVA design with the 2 beverages x 5 time periods (fast, 30, 60, 90, 120 min post-consumption) was applied to assess the comparative effects of the two beverages on the measured variables. Two-tailed, paired t -test was applied for the evaluation of differences between baseline conditions before regular and decaffeinated coffee consumption. Total response of measured variables to regular and decaffeinated coffee consumption during the period of 120 min was evaluated by the area under the curve. All variables were tested for homogeneity of variance and normal distribution before any statistical analysis was applied. Data are expressed as mean +/- S.D. unless otherwise stated and p < 0.05 was considered statistically significant.
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How many outcome-specific endpoints are evaluated? 3
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What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately) Blood pressure (central [aortic] and peripheral [brachial] SBP and DBP)
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List additional health endpoints (separately). 2 Heart rate
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List additional health endpoints (separately).3 Wave reflection (Augmentation Index [AI] and arrival time [delta-t])
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List additional health endpoints (separately).4
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List additional health endpoints (separately).5
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List additional health endpoints (separately).6
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Clinical, physiological, other Physiological
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What is the study design? Controlled Trial
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Randomized or Non-Randomized? RCT
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What were the diagnostics or methods used to measure the outcome? Objective
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Optional: Name of Method or short description Peripheral blood pressures were measured at the brachial artery via the detection of Korotkoff sounds using a sphygmomanometer placed around the nondominant upper arm. Central blood pressures were estimated noninvasively by using a fully automated and validated system (AtCor Medical, Sydney, Australia). [NOTE: Data for AI and delta-t also derived from this instrument.]
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Caffeine (general) Caffeine (general)
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Coffee, Chocolate, energy drink, gum, medicine/supplement, soda, tea, other? Coffee
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Measured or self reported? Measured
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Children, adolescents, adults, or pregnant included? Adults
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What was the reference, comparison, or control group(s)? (e.g. high vs low consumption, number of cups, etc.) Subjects served as their own controls (baseline and decaffeinated coffee)
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What were the listed confounders or modifying factors as stated by the authors? (e.g. multi-variable components of models.  Copy from methods) None
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What conflicts of interest were reported? No information provided
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Refid 15708175
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What were the sources of funding? No information provided
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Results & Comparisons

No Results found.