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Study Title and Description

Caffeine affects cardiovascular and neuroendocrine activation at work and home.



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 Caffeine affects cardiovascular and neuroendocrine activation at work and home.
Author JD Lane,CF Pieper,BG Phillips-Bute,JE Bryant,CM Kuhn,
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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 was conducted to investigate the effects of typical patterns of caffeine consumption on ambulatory measures of cardiovascular and stress-related humoral activity during the day at work and at home in the evening.
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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 Forty-seven healthy male (N=27) and female (N=20) employees of Duke University and surrounding businesses participated in the study. They were recruited by advertisements placed in campus newspapers and handbills posted throughout the medical center and campus. All volunteers were normotensive (blood pressure <140/90 mm Hg) adults who worked in relatively sedentary office and laboratory positions. All were habitual coffee drinkers (2–7 cups daily). Coffee consumption was confirmed by completion of a 7-day diary of caffeinated beverage consumption. Ages ranged from 22 to 45 years. Women who used oral contraceptive steroids and cigarette smokers were excluded. Experimental Design and Treatments The study used a double-blind, placebo-controlled crossover design, in which a controlled dose of caffeine and a placebo were administered in single-day trials to each participant. The experimental caffeine and placebo treatments were presented in randomized counter-balanced order. A fixed dose of 500 mg of caffeine per day was chosen to represent moderate adult caffeine consumption, roughly equivalent to 32 oz. (950 ml) of brewed coffee. The Duke University Medical Center Pharmacy prepared identical #2 hard gelatin capsules that contained 250 mg of caffeine plus dextrose filler or dextrose filler alone. The participant swallowed the first capsule in the laboratory before the start of monitoring (0730–0830 hours) and the second capsule roughly 4 hours later at midday. All caffeine was consumed before 1300 hours. The standardized dosing schedule was intended to simulate the expected patterns of caffeine ingestion in moderate coffee drinkers. Ambulatory Monitoring Study days were scheduled with at least 1 day intervening. All ambulatory studies were scheduled for workdays from Monday to Thursday to maintain consistency in evening home activities. Vigorous physical exercise was banned on study days. Otherwise, participants were instructed to pursue their usual activities at work and at home and not to change their behaviors to accommodate the monitoring procedures. Each ambulatory study began in the early morning after overnight abstinence from all sources of caffeine. The Accutracker II monitor (Suntech Medical Instruments, Raleigh, NC) was used for ambulatory blood pressure and heart rate measurements. The validity of this device for the measurement of blood pressure and heart rate has been established. During the instrumentation of each participant, blood pressure readings from the monitor were compared with simultaneous auscultatory readings taken by the study technician. Valid monitor operation was assumed when the averages of five readings by each method agreed within 5 mm Hg. The Accutracker monitor was programmed to collect measurements four times each hour, with random variation in timing, and to repeat measurements when artifacts were detected. Study participants wore the monitor until bedtime or at least 10 PM, then turned it off and removed the cuff, microphone, and electrodes when preparing for bed. Ambulatory measurements were not collected overnight. Study participants were instructed to complete a brief "diary" entry at the conclusion of each blood pressure measurement. They recorded the time of measurement (as displayed on the monitor), entered single-letter codes to designate their current location (work, home, travel, or other) and their posture (sitting, standing, lying down, or walking), and made numerical ratings of their physical activity and perceived stress during the minutes before the measurement. Entries were made on a single preprinted 4- by 6-inch index card that included sufficient space for the entire day’s measurements. Urine collection was performed for the measurement of catecholamine and cortisol excretion. One sample was collected during the workday, from the start of ambulatory measurements until the end of the workday. A second sample was collected during the evening at home, beginning at the end of the workday and continuing until bedtime. Samples were collected into 1-liter plastic containers that were kept cold in an insulated bag. Participants were instructed to begin each collection period with an empty bladder, to collect all urine excreted during each of the three time periods, and to completely empty the bladder into the container at the conclusion of each sample interval. They were also instructed to increase caffeine-free fluid consumption throughout the day to ensure adequate urine production. The volumes of urine samples were recorded, and small aliquots were frozen at -20°C until assays were performed. Ambulatory BP and HR measurements were independently inspected by two investigators (JDL and CFP), and readings were deleted by consensus when error codes indicated significant artifacts in the measurement. When a programmed measurement was deleted, the retry value was used if possible. However, if the suspect measurement was judged satisfactory, the retry value was deleted from the data file to prevent oversampling of that time point. Urinary-free catecholamines were measured by high-performance liquid chromatography using electrochemical detection. Urinary creatinine was measured using the Jaffe method as modified by Slot. Values of catecholamines were adjusted for the creatinine content of each urine sample. Data Analysis Data were analyzed using regression models containing both fixed and random effects, a technique labeled hierarchical regression or mixed models. The hierarchical regression analysis was conducted using Proc Mixed (SAS Version 8, SAS Institute, Cary, NC). Statistical significance was declared when p </= 0.05. The hierarchical regression analysis provided estimates of means and slopes for the different fixed effects and interactions.
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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) Blood pressure (SBP, DBP)
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List additional health endpoints (separately). 2 Heart Rate
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List additional health endpoints (separately).3 Urinary catecholamines (epinephrine and norepinephrine)
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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 The Accutracker II monitor (Suntech Medical Instruments, Raleigh, NC) was used for ambulatory blood pressure and heart rate measurements. Urinary-free catecholamines were measured by high-performance liquid chromatography using electrochemical detection.
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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.) Each subject served as his/her own control
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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) Posture (seated, standing, walking, lying down); activity (scale of 1 to 5); stress (scale of 1 to 5)
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What conflicts of interest were reported? No information provided
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Refid 12140349
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What were the sources of funding? Research supported by National Institutes of Health Grant R01 HL51634.
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Results & Comparisons

No Results found.