Study Preview
Study Title and Description
Dietary caffeine consumption and withdrawal: confounding variables in quantitative cerebral perfusion studies?
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 | Dietary caffeine consumption and withdrawal: confounding variables in quantitative cerebral perfusion studies? |
| Author | AS Field,PJ Laurienti,YF Yen,JH Burdette,DM Moody, |
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| Year | 2003 |
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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)? | The purpose of our investigation was to evaluate the effects of dietary caffeine intake and withdrawal on CBF, as determined from a randomized, blinded, placebo-controlled study. |
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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 and Study Design Twenty healthy adult volunteers (16 men, four women; age range, 24–64 years) participated in the study with the following inclusion criteria: no history of migraines, stroke, hypertension, diabetes mellitus, or any neurologic or vascular disease; no history of alcohol or drug abuse; and no use of tobacco products or oral contraceptives. None of the female subjects was taking hormone replacement therapy. The subjects’ average daily caffeine intake was estimated from their responses to a dietary questionnaire and published data on the caffeine content of common beverages. Subjects were then categorized according to their caffeine use as "low" (<125 mg/d; mean, 41 mg/d) users (10 subjects) or "high" (>300 mg/d; mean, 648 mg/d) users (10 subjects). Subjects were recruited by means of solicitation of high and low caffeine users; volunteers reporting intermediate caffeine use were excluded. Each subject underwent quantitative perfusion MR imaging on two separate days at the same time of day and with matching conditions. However, there was one exception: At 60–90 minutes before imaging, subjects received an oral dose of either caffeine (250 mg, equivalent to two to three cups of coffee) or placebo. Subjects were randomized to receive caffeine on one day and placebo on the other in a single-blind counterbalanced design. Administration of all doses of caffeine or placebo was preceded by at least 30 hours of caffeine abstinence such that the placebo condition would likely reflect a state of withdrawal in the high caffeine users. Imaging Protocol, Image Processing and Statistical Analysis Experiments were conducted with a 1.5-T MR imaging unit (Echo-speed Horizon LX; GE Medical Systems, Milwaukee, Wis) with a birdcage head coil. Image reconstruction and postprocessing were accomplished at a workstation (UltraSPARC; Sun Microsystems, Santa Clara, Calif) with mathematical software (MATLAB, Mathworks, Sherborn, Mass; IDL, Research Systems, Boulder, Colo). Mean CBF values were then calculated separately for the white matter (WM), anterior circulation gray matter (AGM), and posterior circulation GM (PGM). The CBF data were analyzed by using two-way analysis of variance with repeated measures on the treatment factor (caffeine vs placebo). This design tested within-subject differences between caffeine and placebo, between-subject differences related to level of dietary caffeine use, and interaction effects between dietary caffeine use and caffeine-induced CBF response. In addition, since the categorization of subjects into low– and high–caffeine use groups was necessarily somewhat arbitrary, linear regression was used to test whether the subjects’ dietary caffeine habits predicted either their CBF in the placebo condition or the relative magnitude of their CBF response to caffeine. The criterion for statistical significance was chosen as a P value of .05 or less for all tests. |
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| How many outcome-specific endpoints are evaluated? | 1 |
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| What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately) | Cerebral blood flow (white matter [WM], anterior circulation gray matter [AGM], posterior circulation gray matter [PGM]) |
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| List additional health endpoints (separately). 2 |
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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 | Experiments were conducted with a 1.5-T MR imaging unit (Echo-speed Horizon LX; GE Medical Systems, Milwaukee, Wis) with a birdcage head coil. Image reconstruction and postprocessing were accomplished at a workstation (UltraSPARC; Sun Microsystems, Santa Clara, Calif) with mathematical software (MATLAB, Mathworks, Sherborn, Mass; IDL, Research Systems, Boulder, Colo). |
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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.) | Subjects served as their own controls (placebo) |
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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) | Self-reported dietary caffeine use (low [<125 mg/day] or high [>300 mg/day]) |
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| What conflicts of interest were reported? | No information provided |
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| Refid | 12616005 |
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| What were the sources of funding? | Supported in part by a grant from the Charles A. Dana Foundation. |
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Results & Comparisons
No Results found.
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