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Study Title and Description

Gender differences in subjective and physiological responses to caffeine and the role of steroid hormones



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 Gender differences in subjective and physiological responses to caffeine and the role of steroid hormones
Author J. L. Temple and A. M. Ziegler
Country
Year 2011
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 purpose of the study presented here was to determine if gender differences in the subjective and physiological effects of caffeine are related to levels of circulating steroid hormones.
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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) Participants and Recruitment Participants were 15 males and 9 females with an average age of 15.6 – 0.12 years, recruited through direct mailings, flyers distributed at local middle and high schools, as well as flyers posted around the University at Buffalo and the surrounding community. Eligibility criteria included the following: previous ingestion of caffeine without adverse reactions, having signs of pubertal maturation, not using hormone based contraceptives, not smoking, not taking medication known to have interactions with caffeine, and willingness to visit the laboratory on four occasions for 90 minutes each. General Experimental Procedures Qualifying males were scheduled for four visits, 2 weeks apart. Females were asked to schedule their first and third visits to our laboratory within 3–8 days from day 1 of menstruation (follicular phase). Their second and fourth visits were scheduled 2 weeks later (luteal phase). Participants were provided a list of caffeine-containing products from which to abstain for 24 hours before their scheduled appointment and were instructed not to not eat or drink anything other than water for 2 hours before the session. Participants were also asked to refrain from engaging in physical activity on the day of each laboratory visit. To remove subject expectations about the effects of caffeine, participants were told that the beverage they would be consuming ‘‘may have levels of one or more of the following substances manipulated: sugar, aspartame, Splenda, caffeine, or artificial coloring.’’ This deception was considered acceptable because it involved no greater than minimal risk, and was necessary to prevent potential preconceptions of caffeine’s effects from altering experimental results. Participants then completed a same-day and previous-day dietary recall to confirm caffeine abstinence. Participants then provided a 3-mL saliva sample into a sterile tube that was analyzed for steroid hormones. Next, the participant completed the ‘‘caffeine consumption questionnaire’’ to determine caffeine use habits. The participant then had baseline blood pressure and heart rate readings taken. Then, the participant consumed a 350mL portion of Sprite, lemonade, or orange juice, containing either placebo or caffeine (2 mg/kg). Participants received two doses each of placebo and caffeine over the course of four separate visits. Before the first visit, participants were randomized to receive caffeine or placebo first and subsequent drug administration was counterbalanced. Immediately after beverage consumption, blood pressure and heart rate measurements were taken every 10 minutes for a total of 60 minutes while participants watched a video. Caffeine and beverage preparation Caffeine and placebo treatments were prepared by an experimenter who was not involved in the data collection for this study. Caffeine was added to Sprite to mask its bitter taste and heated to 140oF and stirred for 25 minutes. Flattened Sprite without added caffeine was used as the placebo. The caffeine or placebo solutions were then aliquoted into 14-mL vials, labeled A or B, and frozen. On the day of the visit, the appropriate vial was thawed for >1 hour at room temperature. Participants were able to choose to drink orange juice, lemonade, or Sprite, which are all caffeine free. We verified that this dose of caffeine could not reliably be detected by taste in a previous study. While the participant was providing a saliva sample and completing questionnaires, the researcher prepared a mixture of 350mL of the chosen beverage and volume of A or B equivalent to 2mg caffeine/kg body weight. Measurements - Cardiovascular Responses An automated heart rate and blood pressure monitor (Tango; SunTech Medical, Inc., Morrisville, NC) was used to collect cardiovascular measurements. The participants were seated in reclined position and instructed to relax. The blood pressure cuff was placed on the nondominant arm, with the microphone positioned over the brachial artery. Electrodes were placed on each forearm and on the chest above the heart. A baseline reading was conducted before consumption of the test beverage. Immediately after caffeine or placebo consumption, blood pressure and heart rate readings were taken every 10 minutes for 60 minutes. Caffeine Consumption Average daily caffeine consumption was calculated based on the participant’s self-report of daily or weekly intake of caffeine on a ‘‘caffeine use questionnaire’’ adapted from Miller that was designed to assess sources, amounts, and frequency of caffeinated food and beverage intake as well as reasons why adolescents use and/or do not use caffeine. Amounts of caffeine contained within each major source were calculated based on information from the U.S. Department of Nutritional Services and include the following: tea (40mg/5 oz), soda (40mg/12 oz), coffee (100mg/5 oz), energy drinks (*150 mg/12 oz), chocolate (10mg/oz), and caffeine-containing pills (Excedrin or No-Doze–130 mg–200mg/pill). Analytic Plan Gender differences in caffeine consumption were analyzed using a one-way analysis of variance. The pattern of diastolic blood pressure (DBP) and systolic blood pressure (SBP), and heart rate were analyzed using mixed effects regression models with gender, and caffeine use (mg/day) as time invariant predictors and time (from 10 to 60 minutes after drug administration), drug treatment (placebo vs. caffeine), and steroid hormone levels as time variant predictors and baseline blood pressure and heart rate as covariates. Cardiovascular response data were considered significantly different if p < 0.05 and data analyses were conducted using SYSTAT 11.0 (Chicago, IL).
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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) Blood pressure (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
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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 An automated heart rate and blood pressure monitor was used to collect cardiovascular measurements.
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Caffeine (general) Caffeine (general)
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Coffee, Chocolate, energy drink, gum, medicine/supplement, soda, tea, other? Tea
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Measured or self reported? Measured
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Children, adolescents, adults, or pregnant included? Adolescents
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What was the reference, comparison, or control group(s)? (e.g. high vs low consumption, number of cups, etc.) Each participant served as his/her own control (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) Steroid hormone levels
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What conflicts of interest were reported? Neither author of this article has any conflicts of interest to report.
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Refid 10472
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What were the sources of funding? This research was supported by a grant from the National Institute on Drug Abuse (KO1DA021759) to J.L.T.
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Results & Comparisons

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