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Study Title and Description

Effects of caffeine and stress on biomarkers of cardiovascular disease in healthy men and women with a family history of hypertension.



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 Effects of caffeine and stress on biomarkers of cardiovascular disease in healthy men and women with a family history of hypertension.
Author JM Bennett,IM Rodrigues,LC Klein,
Country
Year 2013
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 connection between caffeine and its potentially detrimental effects on blood markers of cardiovascular disease (CVD) are controversial. Most studies have focused on cholesterol as a putative mediator of the caffeine–CVD relationship. Other blood markers such as C-reactive protein (CRP) and fibrinogen have been understudied. We examined the effects of caffeine and psychological stress on these CVD markers in healthy, young men and women with a confirmed family history of hypertension.
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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: Healthy men (N= 26) and women (N= 26), between the ages of 18 and 29 years (21.4_0.3 years), were recruited to participate in a study on the biobehavioral effects of caffeine through the use of flyers posted around the Penn State campus and local community. A trained researcher initially interviewed potential participants over the telephone to review their health history and to determine eligibility for an initial screening lab session, including the need to have a biological parent under current treatment for high BP. Family history of hypertension status was confirmed by a questionnaire completed by the potential participant’s biological parent(s) and returned directly to the laboratory in a pre-paid, lab addressed envelope; family history of hypertension was defined as having at least one parent who was (1) diagnosed with hypertension and (2) currently taking or had taken prescription BP regulation medication in the past year (al’Absi et al., 1998; Greenberg & Shapiro, 1987). Laboratory session: The experimental design was a mixed model. The between-subjects’ factors were sex (male and female) and drug administration (placebo and caffeine). The within-subjects factor was stress. Specifically, all participants participated in the same protocol, which consisted of a baseline rest period, a challenge period (13.5-min speech challenge and 15-min mental arithmetic task) and a recovery period. BP and heart rate (HR) were collected every 2 min throughout the laboratory session. Blood samples and self-reported rating of stress using a 7-point Likert scale were collected three times during the study: (1) end of baseline period and immediately prior to the stress protocol, (2) 15 min following completion of the stress protocol and (3) 45 min after the stressor ended. A standard BP cuff (Dinamap Compact Blood Pressure Monitor, Critikon, Tampa, FL) was used. Drug administration: At the end of the 30-min baseline period, anhydrous caffeine (3.3 mg/kg) (Spectrum Chemical Corporation, Gardena, CA) mixed with refrigerated white grapefruit juice (Unsweetened White Grapefruit Juice, Giant brand, Landover, MD) was administered to half of the participants. Caffeine dosage was calculated on the basis of the participant’s body weight obtained at the beginning of the laboratory session. The placebo group received grapefruit juice without the addition of caffeine. The caffeine dosage and use of grapefruit juice has consistently been used in the administration of caffeine in other studies (e.g. Hartley et al., 2000; Lovallo et al., 1989, 1991). Grapefruit juice has been found to have no effect on caffeine’s pharmacokinetics and no hemodynamic effects (Maish, Hampton, Whitsett, Shepard, & Lovallo, 1996), and it was used to mask the bitter taste of caffeine. Stressor: All participants underwent a modified Trier Social Stress Task protocol (Kirschbaum, Pirke, & Hellhammer, 1993) that consisted of preparation (10 min) and delivery of a 3.5 min videotaped speech about a personal failure, followed by 12 min of mental serial subtraction task under time pressure with negative feedback (i.e. counting backwards from a four digit number by 7’s and then 13’s). This portion of the study was conducted by a different experimenter (LCK), whom the participant believed to be a psychologist that was evaluating his or her performance on the tasks. Participants also were told that the videotaped speech would be evaluated by a panel of psychologists. Assays: C-reactive protein levels were assessed using an enzyme linked immunosorbent assay (ELISA) kit developed in-house at the GCRC (DakoCytomation, Glostrup, Denmark) that has a minimum sensitivity of 3.9 ng/mL and upper range of 4000 ng/mL. Fibrinogen levels were assessed using an ELISA (Affinity Biologicals, Inc., Ancaster, Ontario, Canada); this kit has a minimum sensitivity of 0.003 mg/mL and an upper limit of 200 mg/mL.
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How many outcome-specific endpoints are evaluated? 3
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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 Serum C-reactive protein
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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 A standard BP cuff (Dinamap Compact Blood Pressure Monitor, Critikon, Tampa, FL) was used. C-reactive protein levels were assessed using an enzyme linked immunosorbent assay (ELISA) kit developed in-house at the GCRC (DakoCytomation, Glostrup, Denmark) that has a minimum sensitivity of 3.9 ng/mL and upper range of 4000 ng/mL. Fibrinogen levels were assessed using an ELISA (Affinity Biologicals, Inc., Ancaster, Ontario, Canada); this kit has a minimum sensitivity of 0.003 mg/mL and an upper limit of 200 mg/mL.
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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 vs. 3.3 mg/kg caffeine.
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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) Study exclusion criteria included any significant health problems or use of medications that would interfere with interpretation of BP and blood marker data such as diabetes or hypertension, laboratory resting SBP>140mmHg or DBP>90 mmHg, body mass index (kg/m2) >30, documented neurological disorder, history of depression and/or anxiety, cognitive or attentional disorders such as attention deficit/hyperactivity disorder, drug or medication use that would interfere with normal hormonal, metabolic and cardiovascular functioning, including oral and injected corticosteroids, psychostimulants, aspirin, antioxidant vitamins or use of tobacco or other nicotine products and daily caffeine consumption <100 mg (about one 8-oz. cup of coffee) or >500 mg. For female participants, women were excluded if they used hormonal medication, current or recent (<1 year) pregnancy, or current or recently breastfeeding. Using published methods from both our lab and others, women were brought into the laboratory during the late luteal phase of their menstrual cycle as determined by self-reported date of the last menstrual period and menstrual cycle length (Kirschbaum et al., 1999;Walter et al., 2012;Whetzel et al., 2007). The luteal phase also was confirmed through baseline serum samples that were assayed for estradiol (165.21 + 21.72 pg/mL) and progesterone (27.12 + 4.66 ng/mL). All women included in this study were in the appropriate phase of their menstrual cycle. The study design comprised a 2 (sex)_2 (caffeine, placebo) design. To ensure all baseline characteristics were equally distributed among groups, two-way analyses of variance (ANOVA) tested continuous data and w2 analyses were used for categorical data. Ethnicity data was collapsed to Whites and all minorities to meet w2 assumptions that no cells expected count should be less than 5. Separate repeated-measures ANOVA were conducted to test the effects of sex and caffeine on BP, HR, cortisol, fibrinogen, and CRP across the laboratory session. Separate ANOVAs were used to test any significant group X time interactions. Cortisol, fibrinogen, and CRP data were natural log transformed to normalize their distribution (Walter et al., 2012; Whetzel et al., 2006). SBP, DBP, and HR were averaged across each time period (i.e. baseline, stress and recovery) as described by Llabre and colleagues (1988).
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What conflicts of interest were reported? "None of the authors have competing financial interests to disclose."
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Refid 23504818
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What were the sources of funding? This work was supported by the Penn State Internal Funds (LCK), the Penn State Hintz Graduate Education Enhancement Fellowship (IMR), the Office of Naval Research (N00014-03-1-0248) and The Pennsylvania State University General Clinical Research Center (NIH Grant M01 RR 10732).
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Results & Comparisons

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