JAMA : the journal of the American Medical Association
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JAMA
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The relative merits of various study designs and their placement in hierarchies of evidence are often discussed. However, there is limited knowledge about the relative citation impact of articles using various study designs. ⋯ Overall, the citation impact of various study designs is commensurate with most proposed hierarchies of evidence.
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Review Meta Analysis
Fracture prevention with vitamin D supplementation: a meta-analysis of randomized controlled trials.
The role and dose of oral vitamin D supplementation in nonvertebral fracture prevention have not been well established. ⋯ Oral vitamin D supplementation between 700 to 800 IU/d appears to reduce the risk of hip and any nonvertebral fractures in ambulatory or institutionalized elderly persons. An oral vitamin D dose of 400 IU/d is not sufficient for fracture prevention.