Advanced Search

Study Preview



Study Title and Description

Acute effect of black and green tea on aortic stiffness and wave reflections.



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?
  • Comments Comments (
    0
    ) |

Primary Publication Information
  • Comments Comments (
    0
    ) |
TitleData
Title Acute effect of black and green tea on aortic stiffness and wave reflections.
Author C Vlachopoulos,N Alexopoulos,I Dima,K Aznaouridis,I Andreadou,C Stefanadis,
Country
Year 2006
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
  • Comments Comments (
    0
    ) |
What is the objective of the study (as reported by the authors)? The present randomized, sham procedure-controlled, cross-over (three arm) study was undertaken to evaluate the acute effects of both black and green tea on arterial stiffness and wave reflections in humans.
  • Comments Comments (
    0
    ) |
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) Study Population The study population consisted of 29 healthy individuals studied on three separate occasions each, in two sub-studies; the black tea study (16 subjects, mean age 31.0 years, range 25 to 38, 10 men) and the green tea study (13 subjects, mean age 30.8 years, range 26 to 34, 7 men). All subjects in both studies were nonobese (BMI < 27 kg/m2) and they did not have hypertension, diabetes, hyperlipidemia, or family history of premature vascular disease. Seven subjects in the black tea study and five in the green tea study were smokers. They were clinically well and taking no regular cardiovascular medications or antioxidant vitamin supplementation. Subjects abstained from caffeine and ethanol intake for at least 12 hours and from flavonoid-containing food for at least 24 hours before each session. Female participants were examined during the follicular phase of menstrual cycle and none was on oral contraceptives. Study Design Each sub-study was carried out using a randomized (sequence of exposure), single-blind (operator), sham-procedure-controlled, cross-over (tea-caffeine-placebo) design. Black Tea Study: The 16 subjects of this study arm were studied on three separate days on which they took either: a) 6 gm of black tea (Lipton Inc.) added in 450 ml of boiled water for 5 min, or b) 175 mg of caffeine (the amount contained in 6 gm of black tea, see below "measurement of caffeine content in tea") diluted into 450 ml of boiled water, or c) 450 ml of boiled water. Green Tea Study: The 13 subjects of this study arm were also studied on three separate days on which they took either: a) 6 gm of green tea (Lipton Inc.) added in 450 ml of boiled water for 5 min, or b) 125 mg of caffeine (the amount contained in 6 gm of green tea, see below "measurement of caffeine content in tea") diluted into 450 ml of boiled water, or c) 450 ml of boiled water. Measurements were obtained in a quiet, temperature-controlled room at 23°C, while the subjects had fasted for at least 8 hours. After a 20-min rest period in the supine position baseline measurements for evaluation of arterial elastic properties were taken. Then, the subjects were randomized to the different arms of the study and measurements were repeated at 30, 60, 90, 120, 150, and 180 min after baseline measurements. Evaluation of Aortic Elastic Properties Carotid-femoral pulse wave velocity (PWV), an established index of aortic stiffness, was calculated from measurements of pulse transit time and the distance traveled between two recording sites (pulse wave velocity = distance [meters]/transit time [seconds]) using a validated non-invasive device (Complior®, Artech Medical, Pantin, France), which allows online pulse wave recording and automatic calculation of pulse wave velocity. Two different pulse waves were obtained simultaneously at two sites (at the base of the neck for the common carotid and over the right femoral artery) with two transducers. Measurement of Wave Reflection Indices Augmentation index (AIx) and augmented pressure of the central (aortic) pressure waveform were measured as indices of wave reflections. Augmentation index (AIx) was measured by using a validated, commercially available system (SphygmoCor ®, AtCor Medical, Sydney, Australia), which employs the principle of applanation tonometry and appropriate acquisition and analysis software for non-invasive recording and analysis of the arterial pulse. In brief, from radial artery recordings, the central (aortic) arterial pressure was derived with the use of a generalized transfer function which has been shown to give an accurate estimate of the central arterial pressure waveform and its characteristics [15,30 –32]. Waveforms of radial pressure were calibrated according to sphygmomanometric systolic and diastolic pressure measured in the brachial artery. Statistical Analysis Numerical data are expressed as the mean +/- SEM. All variables were tested for homogeneity of variance and normal distribution, before any statistical analysis was applied. Baseline parameters between the three sessions were compared using one-way ANOVA. In order to evaluate the composite effect of the tea, or caffeine versus placebo over time on the variables of interest, an overall 7 x 2 analysis of variance (ANOVA) for repeated measures was performed (7 periods [baseline, 30, 60, 90, 120, 150 and 180 minutes] x 2 interventions [tea or caffeine versus placebo]). A P value _0.05 was considered statistically significant. Data analysis was performed using the SPSS statistical package for Windows (version 10.0, SPSS Inc., Chicago, Illinois).
  • Comments Comments (
    0
    ) |
How many outcome-specific endpoints are evaluated? 4
  • Comments Comments (
    0
    ) |
What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately) Blood pressure (central [aortic] and peripheral [brachial] SBP and DBP)
  • Comments Comments (
    0
    ) |
List additional health endpoints (separately). 2 Heart rate
  • Comments Comments (
    0
    ) |
List additional health endpoints (separately).3 Aortic stiffness (pulse wave velocity [PWV])
  • Comments Comments (
    0
    ) |
List additional health endpoints (separately).4 Wave reflection (augmentation index [AIx] and augmentation pressure [AP])
  • Comments Comments (
    0
    ) |
List additional health endpoints (separately).5
  • Comments Comments (
    0
    ) |
List additional health endpoints (separately).6
  • Comments Comments (
    0
    ) |
Clinical, physiological, other Physiological
  • Comments Comments (
    0
    ) |
What is the study design? Controlled Trial
  • Comments Comments (
    0
    ) |
Randomized or Non-Randomized? RCT
  • Comments Comments (
    0
    ) |
What were the diagnostics or methods used to measure the outcome? Objective
  • Comments Comments (
    0
    ) |
Optional: Name of Method or short description PWV was calculated from measurements of pulse transit time and the distance traveled between two recording sites using a validated non-invasive device (Complior®, Artech Medical, Pantin, France). AIx was measured by using a validated, commercially available system (SphygmoCor ®, AtCor Medical, Sydney, Australia). Waveforms of radial pressure were calibrated according to sphygmomanometric systolic and diastolic pressure measured in the brachial artery.
  • Comments Comments (
    0
    ) |
Caffeine (general) Caffeine (general)
  • Comments Comments (
    0
    ) |
Coffee, Chocolate, energy drink, gum, medicine/supplement, soda, tea, other? Tea
  • Comments Comments (
    0
    ) |
Measured or self reported? Measured
  • Comments Comments (
    0
    ) |
Children, adolescents, adults, or pregnant included? Adults
  • Comments Comments (
    0
    ) |
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
  • Comments Comments (
    0
    ) |
What were the listed confounders or modifying factors as stated by the authors? (e.g. multi-variable components of models.  Copy from methods) None
  • Comments Comments (
    0
    ) |
What conflicts of interest were reported? No information provided
  • Comments Comments (
    0
    ) |
Refid 16766780
  • Comments Comments (
    0
    ) |
What were the sources of funding? No information provided
  • Comments Comments (
    0
    ) |




Results & Comparisons

No Results found.