Study Preview
Study Title and Description
Habitual coffee and tea drinkers experienced increases in blood pressure after consuming low to moderate doses of caffeine; these increases were larger upright than in the supine posture.
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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| Title | Habitual coffee and tea drinkers experienced increases in blood pressure after consuming low to moderate doses of caffeine; these increases were larger upright than in the supine posture. |
| Author | MK McMullen,JM Whitehouse,G Shine,A Towell, |
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| Year | 2011 |
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Secondary Publication Information
There are currently no secondary publications defined for this study.
Extraction Form: Cardiovascular Design
| Question... Follow Up | Answer | Follow-up Answer | |
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| 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)? | This study investigated a group of habitual caffeine users following their self-determined consumption pattern involving two to six servings daily. |
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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) | The interventions were either a placebo capsule or caffeine capsules at the levels of 67, 133 and 200 mg. It was estimated that the 67 mg dose would be approximately the equivalent of 1 mg/kg, the 133 mg dose the equivalent of 2 mg/kg and the 200 mg dose the equivalent of 3 mg/kg. The capsules were identical and contained varying combinations of caffeine and microcrystalline cellulose together as well as magnesium stearate. Finometer recordings were obtained pre-intervention and postintervention at both 30 and 60 min. Each recording segment commenced with a five minute relaxation period in the supine posture after which 90 s Finometer recordings were obtained first in the supine posture and later standing. To avoid orthostatic influences, the standing posture recording started 90 s after the participant began to change posture. Participants were tested without any attempt to control caffeine intake other than to maintain their normal consumption which was verbally confirmed at the beginning of each test session. The Finometer (FMS, Finapres Measurement Systems, Amsterdam, The Netherlands) finger pulse contour recordings together with the accompanying Modelflow software provide the parameters: heart rate, ejection time, dp/dt (contraction force), DPTI/SPTI (the cardiac oxygen supply: demand ratio (the Buckberg index)), stroke volume, cardiac output, systolic,diastolic and mean blood pressure, peripheral resistance, arterial compliance and aortic impedance. Additionally the body surface area adjusted values (Dubois and Dubois formula): indexed stroke volume, indexed cardiac output (cardiac index) and indexed peripheral resistance values are provided. The following parameters are reported: heart rate, ejection time, dp/ dt, DPTI/SPTI, cardiac index, systolic pressure, diastolic pressure, arterial compliance, aortic impedance and indexed peripheral resistance. |
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| How many outcome-specific endpoints are evaluated? | 2 |
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| What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately) | Heart rate |
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| List additional health endpoints (separately). 2 | Blood pressure |
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| List additional health endpoints (separately).3 |
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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 | Finometer recordings were obtained pre-intervention and postintervention at both 30 and 60 min. Each recording segment commenced with a five minute relaxation period in the supine posture after which 90 s Finometer recordings were obtained first in the supine posture and later standing. To avoid orthostatic influences, the standing posture recording started 90 s after the participant began to change posture. |
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| Caffeine (general) | Caffeine (general) |
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| Coffee, Chocolate, energy drink, gum, medicine/supplement, soda, tea, other? |
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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.) | Placebo as well as baseline measurements. |
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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) | Hypertensives (systolic pressure >140 mm Hg or diastolic pressure >90 mm Hg), smokers, pregnant women and those on prescribed medication were excluded from the study. Planned contrasts, comparing measures from each caffeine condition with measures from the placebo condition, were analyzed with repeated measures 2 x 2 (pre/post x placebo/caffeine) ANOVA for each posture using SPSS v15 (Chicago, USA). A 2 x 2 x 2 (pre/post x placebo/caffeine x supine/posture) repeated measures ANOVA was used to assess whether the cardiovascular responses to caffeine were influenced by posture. |
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| What conflicts of interest were reported? | The authors reported there were no conflicts of interest. |
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| Refid | 21779579 |
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| What were the sources of funding? | Authors report no funding or sponsoring was involved in this study. |
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Results & Comparisons
No Results found.
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