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Study Title and Description

Caffeine intake increases the rate of bone loss in elderly women and interacts with vitamin D receptor genotypes.



Key Questions Addressed
1 For [population], is caffeine intake above [exposure dose], compared to intakes [exposure dose] or less, associated with adverse effects on bone and calcium balance outcomes?
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Primary Publication Information
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TitleData
Title Caffeine intake increases the rate of bone loss in elderly women and interacts with vitamin D receptor genotypes.
Author PB Rapuri,JC Gallagher,HK Kinyamu,KL Ryschon,
Country
Year 2001
Numbers

Secondary Publication Information
There are currently no secondary publications defined for this study.


Extraction Form: Bone & Calcium Outcomes
Design Details
Question... Follow Up Answer Follow-up Answer
Refid 11684540
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What outcome is being evaluated in this paper? Bone and Calcium
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What is the objective of the study (as reported by the authors)? Our goals were 1) to compare in both a crosssectional study and a 3-y longitudinal study the bone mineral density (BMD) of postmenopausal women consuming high or low amounts of caffeine and 2) to study the interaction between caffeine intake, vitamin D receptor (VDR) polymorphism, and BMD in the longitudinal study.
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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: 489 elderly women aged 66–77 y participated in a double-blind randomized clinical trial (STOP IT: Sites Testing Osteoporosis Prevention or Intervention) that was intended to test the efficacy of 3 therapies in reversing bone loss in the proximal femur and spine compared with placebo. Study design: Cross-sectional: used baseline data for 489 women enrolled in STOP IT. Biochemical indexes and BMD measures were compared between groups with low (≤300 mg/d) and high (> 300 mg/d) caffeine intakes. Longitudinal: data of 96 women who received the placebo treatment and completed the 3-y study were used to compare the low- and high-caffeine groups. Average caffeine intake at baseline and at 3 y was used to divide the women into groups according to caffeine intake, and the percentage change over 3 y (corrected for baseline values) in the biochemical indexes and BMD measures was compared between the low- and high-caffeine groups. The interaction between VDR genotype and caffeine intake was analyzed by using the longitudinal data. Dietary caffeine intake, smoking, and alcohol history: Dietary intake at baseline and at the end of the study (3 y) was assessed by using 7-d food diaries administered by a dietitian. Average daily caffeine and calcium intakes were calculated by using the FOOD PROCESSOR II PLUS nutrition and diet analysis. Calcitropic hormones and bone markers Fasting blood samples and 24-h urine collections were obtained from the subjects at baseline, at 6-mo intervals, and at the end of the study (at 3 y). Serum intact parathyroid hormone was measured with the Allegro immunoradiometric assay. Serum 25-hydroxyvitamin D was assayed with a competitive protein binding assay. Serum concentrations of osteocalcin were measured by radioimmunoassay. Urinary collagen cross-links were measured by enzyme-linked immunosorbent assay. Bone mineral density BMD (in g/cm2) was measured by dual-energy X-ray absorptiometry (model Lunar DPX-L) at the lumbar spine (L1–L4), the total hip, 2 sites in the proximal femur (femoral neck and trochanter), and the whole-body was calculated by using standardized protocols for uniform subject positioning, scan mode, and scan analysis. VDR restriction fragment length polymorphism VDR genotypes were identified as TaqI restriction fragment length polymorphisms by polymerase chain reaction (PCR). The presence of a restriction site for TaqI was genotyped as the t allele and the absence of the restriction site was genotyped as the T allele. Statistical analysis Baseline characteristics of the cross-sectional and longitudinal study populations were compared between caffeine groups by using Student’s t test and between VDR genotypes within caffeine groups by using one-way analysis of variance. For the cross-sectional analysis, biochemical indexes and BMD measurements in the low- and high-caffeine groups were compared by using analysis of covariance (ANCOVA) after adjustment for the fixed effects of smoking and alcohol use, calcium intake, and other significant covariates (ie, age, height, weight, and 25-hydroxyvitamin D concentrations) identified from the correlation analysis. For the longitudinal analysis, the percentage of change in BMD and biochemical indexes over 3 y was compared between the 2 caffeine groups by using ANCOVA after correction for the fixed effects of baseline smoking and alcohol intake, the average total calcium intake, each respective baseline BMD value, and other significant covariates identified from the correlation analysis. In the analysis of the interaction between VDR genotypes, caffeine intake, and BMD, the percentage of change in biochemical indexes and BMD over 3 y between VDR genotypes in the low and high-caffeine groups were compared by using ANCOVA. Fixed effects in this model were baseline smoking, alcohol intake, caffeine intake, and VDR genotype. Covariates were average calcium intake, respective baseline BMD, and other significant covariates identified by the correlation analysis. The percentage of change in biochemical indexes and BMD over 3 y between the VDR genotypes within low- and high-caffeine groups was analyzed by using the ANCOVAs determined above for each caffeine group.
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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) Bone mineral density
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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 BMD with DXA
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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? 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.) <300 mg/d vs >300 mg/day
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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) smoking and alcohol use, calcium intake, and other significant covariates (ie, age, height, weight, and 25-hydroxyvitamin D concentrations)
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What were the sources of funding? Not reported by authors
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What conflicts of interest were reported? Not reported by authors
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Results & Comparisons

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