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Study Title and Description

The cumulative effect of coffee and a mental stress task on heart rate, blood pressure, and mental alertness is similar in caffeine-naïve and caffeine-habituated females.



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 The cumulative effect of coffee and a mental stress task on heart rate, blood pressure, and mental alertness is similar in caffeine-naïve and caffeine-habituated females.
Author MD Kennedy,AV Galloway,LJ Dickau,MK Hudson,
Country
Year 2008
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 overall rationale for this study was 3-fold. First, from a nutritional perspective, it was of great interest to determine if the most common brand and amount of coffee bought in Canada today has any real influence on cardiovascular and alertness measures in females. Second, it was felt that this research would contribute to our understanding of the cardiovascular response to coffee in females who were both caffeine-naïve and caffeine-habituated. Lastly, it was of interest to explore the interrelationship of stress and coffee and how this relationship may change based on one's level of caffeine consumption. Thus, the purpose of this investigation was to examine the heart rate (HR), blood pressure (BP), and mental alertness response to a common-sized coffee available throughout Canada (12 oz., containing approximately 140 mg of caffeine) and whether a mentally stressful task modified this response in adult caffeine-habituated and caffeine-naïve females.
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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: Ten caffeine-naïve (age, 23 ± 5.0 years; height, 168.8 ± 7.8 cm; weight, 63.1 ± 9.5 kg) and 10 caffeine-habituated (age, 25 ± 6 years; height, 169.6 ± 2.7 cm; weight, 61.0 ± 4.9 kg) women participated in this study. Exclusion criteria included high blood pressure (z 140/90 mm Hg), smokers, and women who were pregnant or were postmenopausal. Participants were not asked whether they were on an oral contraceptive for confidentiality reasons. To determine if participants were caffeine-habituated or caffeine-naïve, we asked participants to complete an electronic survey to determine the amount of caffeine beverages consumed in an average week. Participants who reported consumption of caffeine of less than 2 servings per week were assigned to the caffeine-naïve group. Participants who reported consumption of caffeine as a minimum of 2 caffeine servings per day were assigned to the caffeine-habituated group. A serving was defined as single cup, can, or foodstuff ingested after preparation or purchase. All participants were asked to abstain from eating or drinking caffeinated substances 12 hours before the test. Experimental design: The design for this experiment was a single repeated measures balanced design where participants acted as their own controls. The rationale for this design was to allow for a single visit for each participant to the laboratory and to ensure that each participant was provided the same treatment protocol. Upon arrival in the laboratory, participant's height and weight were taken, followed by a baseline measurement of HR (every minute) and blood pressure (in triplicate) and alertness (1 time) for 10 minutes. Participants were then required to consume a 12-oz (350 mL) cup of coffee (with their choice amount of sugar and cream) within a 15-minute period. The amount of sugar and cream was not controlled for; however, the amount of sugar and cream was noted to not be excessive or outside the regular amount one would use in a normal cup of Tim Hortons coffee. After consuming the coffee, participants were required to sit quietly during the post-caffeine absorption period of 50 minutes. Heart rate was then taken every minute for a period of 10 minutes, blood pressure was measured in triplicate during this period (pretest), and mental alertness was measured once. Participants then began the Thurstone Word Fluency Test, which included 2 word tasks lasting a total of 9 minutes. During the test, only HR was recorded every minute. Upon completion of the mental stress task, posttest measurements were taken for HR (every minute), blood pressure (in triplicate), and alertness (1 time) for a 10-minute period. Special considerations: Participants were asked to arrive at the laboratory at 9:00 AM after ingesting a normal breakfast of either toast and juice or cereal and juice. Coffee was purchased from a local Tim Hortons (a national coffee chain that is ubiquitous throughout Canadian culture and landscape) for standardization of caffeine and brewing techniques. Tim Hortons coffee is the most popular coffee purchased in Canada, holding 62% of the market share compared with Starbucks at number 2 position with 7% of the market share. A large (350-400 mL) Tim Hortons coffee contains approximately 140 mg of caffeine (Tim Horton’s website), which is the average amount of caffeine in a normal coffee (Magkos and Kavouras, 2005). Blood pressure recordings were completed by a certified personal trainer (Canadian Society of Exercise Physiology) or a registered nurse to ensure accurate measures and each participant's blood pressure was measured by the same person throughout the entire experimental protocol. Heart rate and blood pressure: Heart rate was measured with wireless HR monitors (Polar Electro Oy, Kempele, Finland) and recorded every minute during assessment periods. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) was taken on the left arm using a standard blood pressure cuff and stethoscope and recorded 3 times in each sampling period (baseline, pretest, and posttest).
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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 (systolic and diastolic)
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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? NCT
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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 Heart rate was measured with wireless HR monitors (Polar Electro Oy, Kempele, Finland) and recorded every minute during assessment periods. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) was taken on the left arm using a standard blood pressure cuff and stethoscope and recorded 3 times in each sampling period (baseline, pretest, and posttest).
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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.) No placebo. Subjects served as their own controls. They were their own baseline.
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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) Heart rate and blood pressure were averaged from the multiple recorded values for each of the sample periods. Two-way repeated measures analyses of variance (2 groups x 3 conditions) determined any differences for HR, blood pressure, and alertness. An independent t test was used to compare the mean task performance (the average score of each group) between the caffeine-naïve and caffeine habituated groups.
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What conflicts of interest were reported? No mention was made of conflicts of interest.
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Refid 19083466
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What were the sources of funding? No mention was made of funding.
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Results & Comparisons

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