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Study Title and Description

Blood pressure response to caffeine shows incomplete tolerance after short-term regular consumption.



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 Blood pressure response to caffeine shows incomplete tolerance after short-term regular consumption.
Author WR Lovallo,MF Wilson,AS Vincent,BH Sung,BS McKey,TL Whitsett,
Country
Year 2004
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 tested whether regular caffeine intake diminishes or abolishes its acute effects on BP in the laboratory.
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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 The study population consisted of 97 healthy adults recruited through advertisement from the general populations of Buffalo, NY and Oklahoma City, Okla. All volunteers were non-obese and in good health by self-report and routine physical examination. They had normotensive BPs (BP <135/85 mm Hg) at screening, regularly consumed 50 to 700 mg/d of caffeine by structured report, were nonsmokers, and used no medications having cardiovascular or metabolic effects. Women were free from oral contraceptives, not lactating, and were not pregnant, as determined by urine pregnancy test (One Step Pregnancy Test; Inverness Medical, Beachwood Park, North Inverness, Scotland). Study Design, Dosing, and Compliance The design was a randomized, placebo-controlled, double-blind, crossover trial of caffeine effects on cardiovascular function that lasted 4 weeks. Each study week included 5 days of home self-administration of placebo (P=0 mg/d) or caffeine (C=300 mg/d or 600 mg/d), followed by 1 laboratory test day (3x250 mg=750 mg) and 1 crossover day (C=100 mg, 0 mg, and 0 mg to buffer sudden changes in intake between study weeks). Home maintenance doses were supplied in bottles of identical gelatin capsules (College of Pharmacy, University of Oklahoma, Oklahoma City) containing either lactose or lactose mixed with 100 mg or 200 mg of USP caffeine (Gallipot, St. Paul, Minn). Subjects were instructed to use one capsule at 8:00 AM, 1:00 PM, and 6:00 PM each day. Test day challenge doses were supplied in capsules containing either lactose or lactose mixed with 250 mg of caffeine administered at 9:00 AM, 1:00 PM, and 6:00 PM. Compliance was assessed by capsule counts in bottles brought in on laboratory days, by caffeine assay of saliva specimens collected at home each day at 7:00 PM (Salivette; Sarstedt, Germany), and from saliva specimens collected each morning on entering the laboratory. Subjects found to be noncompliant by any of these criteria were eliminated from the study and replaced. Laboratory Protocol The laboratory protocol included saliva specimen, breakfast, instrumentation (60 minutes), a rest period (20 minutes), predrug BP baseline (10 minutes), P or C capsule, postdrug response (60 minutes), mental or exercise stress testing (30 minutes), recovery (1 hour), lunch break (1.5 hours), predrug baseline (30 minutes), capsule, postdrug response (1 hour), and ambulatory BP monitoring (18 hours). This report covers the acute BP responses during the 1-hour periods after the 2x250 mg challenge doses administered at 9:00 AM and 1:00 PM. BP was measured during screenings and test sessions using a Dinamap 845 oscillometric vital signs monitor (Critikon, Tallahassee, Fla). During the morning and afternoon caffeine challenges, pressures were measured every 3 minutes during the 10 minutes before using a capsule and during minutes 41 to 60 in the next hour to represent the acute response. The data were then averaged to represent the change from baseline during the 41 to 60 minutes after the challenge combined with the morning and afternoon challenges. Results were analyzed by Student t test, chi-square test, and ANOVA using SAS (SAS System for Windows, ver. 8.2; SAS Institute, Cary, NC) and SPSS (SPSS for Windows, rel. 10.1.0; SPSS, Inc, Chicago, Ill). Potential violation of the sphericity assumption in univariate repeated measures ANOVA was avoided using a multivariate solution for repeated measures factors. For pairwise comparisons, family-wise error rate was controlled across tests at the 0.05 level using Holm sequential Bonferroni procedure. In preliminary analyses, men and women did not differ in their BP responses to challenge doses; therefore, data are presented only for the combined sample.
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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) Blood pressure (SBP and DPB)
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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 BP was measured during screenings and test sessions using a Dinamap 845 oscillometric vital signs monitor (Critikon, Tallahassee, Fla).
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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.) All subjects served as their own controls
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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) High vs. low tolerance
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What conflicts of interest were reported? No information provided
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Refid 14967827
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What were the sources of funding? Supported by the Medical Research Service of the Department of Veterans Affairs and by grants HL 32050, HL 32050-S2, and HL 07640 from the National Heart, Lung, and Blood Institute, Bethesda, Md.
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Results & Comparisons

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