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Study Title and Description

Influence of caffeine on heart rate variability in patients with long-standing type 1 diabetes.



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 Influence of caffeine on heart rate variability in patients with long-standing type 1 diabetes.
Author T Richardson,A Rozkovec,P Thomas,J Ryder,C Meckes,D Kerr,
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 aim of this study was to assess the effect of caffeine on HRV in patients with long-standing type 1 diabetes and healthy control subjects.
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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) Twenty patients with long-standing (> 5 years) type 1 diabetes and 10 control subjects with similar sex and age distribution and without evidence of cardiovascular disease participated in a double-blind, randomized crossover, placebo-controlled study of the effects of caffeine ingestion on HRV. Patients and nondiabetic control subjects had no clinical evidence of autonomic or structural heart disease from history or examination. Patients were screened by 12-lead electrocardiogram (ECG), echocardiography, and treadmill exercise testing. Those with atrial fibrillation, left-bundle branch block, evidence of left ventricular systolic impairment (left ventricular ejection fraction <50%), or exercise-induced ischemia (ST depression >/= 1 mm at >/= 85% maximum predicted heart rate during or after exercise using the Bruce protocol) were excluded. No patients had renal failure. All control subjects had normal beats for at least 99% of total QRS complexes on 24-h ambulatory ECG monitoring. All participants were maintained on a low-caffeine diet (< 50 mg/day) for 2 weeks with either 250-mg caffeine capsules supplemented twice daily (equivalent to average caffeine intake in the U.K.) or matched placebo. At the end of the 2 weeks, HRV was assessed over the last 48 h by continuous Holter monitoring recorded on a miniature digital recorder (Life Card; Reynolds Medical). The patients and control subjects were crossed over to the alternate treatment arm, and the final set of measurements were repeated at the end of a further 2 weeks. Assessment of Autonomic Function The Reynolds Life Card has a crystal-generated time reference track that allowed for recording and replay of speed errors to within 0.5%. Recordings were relayed through a Pathfinder 700 arrhythmia analyzer. After initial arrhythmia assessment, time-domain analyses of HRV were performed. For the purposes of the study, counts of RR interval > 50 ms (sNN50) averaged over the 48-h period were used as a measure of HRV. Frequency domain variables of the HRV were calculated by fast Fourier transformation throughout the whole recording period. A low-pass filter was used to exclude ectopic beats and movement artifacts. A fast Fourier transformation was computed every 5 min of each hour over the 48 h of ECG recording, with the resulting power spectrum corrected for filtering and sampling effects. We calculated the 24-h spectral density and assessed the power with two frequency bands. The low frequency (LF) power (0.04–0.15 Hz) reflects modulation of sympathetic and parasympathetic tone by baroreflex activity, and the high frequency (HF) power (0.15–0.4 Hz) reflects modulation of vagal tone (parasympathetic activity). The LF-to-HF ratio refl ects sympathetic activity. Statistical Analysis Statistical analysis was performed using Excel (Microsoft) and SPSS for Windows version 11. For each individual at the end of each phase of the study, the hourly counts of RR > 50 ms over the 48-h period were summarized by calculating the area under the curve. These summary statistics were then used for the data analysis. RR counts > 50 ms, LF, HF, and the LF-to-HF ratio were assumed to be normally distributed (all Kolmogorov-Smirnov Z statistics had P values of > 0.05). Comparison of changes between caffeine and placebo phases within people with diabetes and healthy control subjects were made using the paired t test, and mean changes were presented with 95% confience intervals. Because there were differences in baseline HRV between the groups, data on HRV has been analyzed using both percentage changes and absolute changes between caffeine and placebo phases. All tests were two tailed and used a 5% critical P value.
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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) Heart rate variability (RR intervals > 50 ms [ssDN50], low frequency power [LF], high frequency power [HF], LF-to-HF ratio)
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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 HRV was assessed over the last 48 h by continuous Holter monitoring recorded on a miniature digital recorder (Life Card; Reynolds Medical).
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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 controls (healthy control arm of study)
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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) None
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What conflicts of interest were reported? No information provided
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Refid 15111532
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What were the sources of funding? This study was supported by an educational grant from the Coffee Science Information Centre. The sponsors had no role in study design, data collection, analysis, or interpretation, or the decision to submit the data for peer review.
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Results & Comparisons

No Results found.