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Study Title and Description

Caffeine consumption and incident atrial fibrillation in women.



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 consumption and incident atrial fibrillation in women.
Author D Conen,SE Chiuve,BM Everett,SM Zhang,JE Buring,CM Albert,
Country
Year 2010
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)? We prospectively assessed the relation between caffeine intake and incident atrial fibrillation.
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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: All study participants were enrolled in the Women’s Health Study, a completed randomized trial that evaluated the risks and benefits of low-dose aspirin and vitamin E in the primary prevention of cardiovascular disease and cancer. Details of the study design have been described previously (19–21). Briefly, beginning in 1993, 39,876 female health professionals in the United States who were age _45 y old and free of cardiovascular disease, cancer, or other major illnesses were randomly assigned to receive 100 mg aspirin every other day, 600 IU vitamin E every other day, both agents, or a placebo. Randomized treatment ended on 31 March 2004, and women were invited to participate in continued observational follow-up, which for the current analysis was truncated on 2 March 2009. Of the original cohort, 4324 women opted out of the observational follow-up. These women were excluded from this analysis because their AF could not be reliably confirmed. However, our findings were very similar in a sensitivity analysis that used self-reported AF events in all women as the main outcome variable to ensure that exclusion of these women did not significantly alter our results (data not shown). We also excluded 1907 women because they either had a history of AF at baseline or did not provide information on beverages and diet, had implausible total energy intakes (,600 or .3500 kcal/d), or left .70 items blank on the food-frequency questionnaire (FFQ) and 7 women because they were subsequently diagnosed with cardiovascular disease before randomization. The final study population for this analysis consisted of 33,638 women. Assessment of caffeine intake: At baseline, 39,310 women (98.6%) in the Women’s Health Study completed a 131-item FFQ, a format that was used and validated in the Nurses’ Health Study (22–24). In 2004, 29,633 (88%) of the 33,638 women included in the current analysis completed a second FFQ. The questionnaire assessed average consumption during the previous year of a specific amount of foods, including coffee, decaffeinated coffee, tea, caffeinated cola, decaffeinated cola, low-calorie caffeinated cola, low-calorie decaffeinated cola, and chocolate, and allowed 9 responses that ranged from never to _6 times/d. Intakes of nutrients and caffeine consumption were calculated by using the US Department of Agriculture food composition data (25) and supplemented by food manufacturers. In these calculations, we assumed that the content of caffeine was 137 mg/cup of coffee, 47 mg/cup of tea, 46 mg/can or bottle of cola, and 7 mg/serving of chocolate candy (4, 26). Validation studies in the Nurses’ Health Study revealed high correlations between self-reported intakes of coffee and other caffeinated beverages assessed by the FFQ and by 4 wk of diet records (r = 0.78 for coffee, r = 0.93 for tea, and r = 0.85 for caffeinated sodas) (22). Coffee was the primary source of caffeine intake (81.3%), with fewer contributions by tea (10.0%), low-calorie caffeinated cola (5.6%), caffeinated cola (1.2%), chocolate (0.3%), and other foods (1.7%). Information on all baseline variables was collected by using mailed questionnaires. Follow-up questionnaires that asked participants about study outcomes and other information were sent every 6 mo during the first year and every 12 mo thereafter. Covariates of interest were self-reported at study entry and included age, body mass index (weight in kilograms divided by the square of height in meters), smoking, blood pressure, history of hypertension, history of hypercholesterolemia, diabetes, parental history of myocardial infarction, alcohol consumption, fish consumption, exercise, and race-ethnicity, which was self reported by the participants as white, black, Hispanic American, Asian American, or other. We updated information for all relevant covariates at the time of the second FFQ administration. Ascertainment of incident AF: Details about the confirmation of AF in the Women’s Health Study have been reported previously (27, 28). In brief, women enrolled in the continued observational follow-up who reported an incident AF event on at least one yearly questionnaire were sent an additional questionnaire to confirm the episode and collect additional information. The women were also asked for permission to review their medical records. For all deceased participants who reported AF during the trial and extended follow-up period, we contacted family members to obtain consent and additional relevant information. An endpoint committee of physicians reviewed medical records for reported events according to predefined criteria. An incident AF event was confirmed if there was electrocardiographic evidence of AF or if a medical report clearly indicated a personal history of AF.
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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) Atrial fibrillation
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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 Clinical
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What is the study design? Cohort
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Randomized or Non-Randomized?
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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 women enrolled in the continued observational follow-up who reported an incident AF event on at least one yearly questionnaire were sent an additional questionnaire to confirm the episode and collect additional information. The women were also asked for permission to review their medical records. For all deceased participants who reported AF during the trial and extended follow-up period, we contacted family members to obtain consent and additional relevant information. An endpoint committee of physicians reviewed medical records for reported events according to predefined criteria. An incident AF event was confirmed if there was electrocardiographic evidence of AF or if a medical report clearly indicated a personal history of AF.
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Caffeine (general)
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Coffee, Chocolate, energy drink, gum, medicine/supplement, soda, tea, other? Coffee, Chocolate, soda, tea
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Measured or self reported? Self-report
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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.) By quintiles of caffeine exposure for the RR for atrial fibrillation. Coffee (decaffeinated and caffeinated): 0 cups/day Tea: 0 cups/day Cola (decaffeinated and caffeinated): 0 cups/day Chocolate: bars or packets/month
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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) We used Spearman correlations to assess the correlation between energy-adjusted caffeine intakes from the 2 FFQs. The main analyses assessed the association between quintiles of caffeine intake and incident AF. Age- and multivariable-adjusted Cox proportional hazards models were constructed to compare hazard ratios and 95% CIs across quintiles of caffeine consumption. For each woman, person-years of follow-up were calculated from the date of return of the baseline questionnaire to the date of first endpoint, death, last follow-up, or to 2 March 2009, whichever came first. Covariates for multivariable models included age, systolic blood pressure, body mass index, hypertension, diabetes, hypercholesterolemia, smoking, exercise, alcohol consumption, parental history of myocardial infarction, treatment group, fish intake, and race-ethnicity. Caffeine intake and other covariates were included in the models as time-varying covariates and updated at the date of the second FFQ in 2004 whenever appropriate. For the 4005 women who did not return the second FFQ, we carried forward their reported caffeine intake at baseline. Women in the lowest category of caffeine consumption were chosen as the reference group for all analyses. In secondary analyses, we assessed the relation between the individual sources of caffeine intake and risk of incident AF, namely caffeinated coffee, decaffeinated coffee, tea, caffeinated cola, decaffeinated cola, low-calorie caffeinated cola, low-calorie decaffeinated cola, and chocolate. Tests for linear and quadratic trends were performed by assigning women the quintile-specific median value of caffeine intake. We tested for deviation from linearity by including quadratic terms in the trend models. We used indicator variables for all covariates that were missing (,2% of missing values for any variable). All analyses were carried out with SAS version 9 software (SAS Institute Inc, Cary, NC).
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What conflicts of interest were reported? None of the authors reported a conflict of interest.
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Refid 20573799
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What were the sources of funding? The authors’ responsibilities were as follows—DC: full access to all study data, integrity of data and accuracy of data analysis, and drafting of the manuscript; DC and CMA: study concept and design; DC, BME, JEB, and CMA: acquisition of data; DC, SEC, and SMZ: statistical analyses; JEB and CMA: obtainment of funding; SMZ: administrative, technical, and material support; CMA: study supervision; and all authors: analysis and interpretation of data and critical revision of the manuscript for important intellectual content. The funding organizations had no role in the design and conduct of the study, the collection, analysis, and interpretation of the data, or the preparation, review, or approval of the manuscript.
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Results & Comparisons

No Results found.