Vitamin D and fractures – 24 meta-analyses and counting

A Case Study of Discordant Overlapping Meta-Analyses: Vitamin D Supplements and Fracture.

PLoS One. 2014 Dec 31;9(12):e115934. doi: 10.1371/journal.pone.0115934. eCollection 2014.

Bolland MJ1, Grey A1.

BACKGROUND:

Overlapping meta-analyses on the same topic are now very common, and discordant results often occur. To explore why discordant results arise, we examined a common topic for overlapping meta-analyses- vitamin D supplements and fracture.

METHODS AND FINDINGS:

We identified 24 meta-analyses of vitamin D (with or without calcium) and fracture in a PubMed search in October 2013, and analysed a sample of 7 meta-analyses in the highest ranking general medicine journals. We used the AMSTAR tool to assess the quality of the meta-analyses, and compared their methodologies, analytic techniques and results. Applying the AMSTAR tool suggested the meta-analyses were generally of high quality. Despite this, there were important differences in trial selection, data extraction, and analytical methods that were only apparent after detailed assessment. 25 trials were included in at least one meta-analysis. Four meta-analyses included all eligible trials according to the stated inclusion and exclusion criteria, but the other 3 meta-analyses "missed" between 3 and 8 trials, and 2 meta-analyses included apparently ineligible trials. The relative risks used for individual trials differed between meta-analyses for total fracture in 10 of 15 trials, and for hip fracture in 6 of 12 trials, because of different outcome definitions and analytic approaches. The majority of differences (11/16) led to more favourable estimates of vitamin D efficacy compared to estimates derived from unadjusted intention-to-treat analyses using all randomised participants.

The conclusions of the meta-analyses were discordant, ranging from strong statements that vitamin D prevents fractures to equally strong statements that vitamin D without calcium does not prevent fractures.

CONCLUSIONS:

Substantial differences in trial selection, outcome definition and analytic methods between overlapping meta-analyses led to discordant estimates of the efficacy of vitamin D for fracture prevention. Strategies for conducting and reporting overlapping meta-analyses are required, to improve their accuracy and transparency.

PMID: 25551377

📄 Download the PDF from VitaminDWiki.

Note: Great trials which included something other than Calcium – such as Magnesium and Vitamin K2 – were not considered in the meta-analyses, as they did not fit in.

See also VitaminDWiki

• Hip fractures reduced 16 to 33 percent by any amount of Vitamin D and Calcium – Oct 2019

• Vitamin D may prevent falls and fractures without Calcium – an overview of 9 meta-analysis – Oct 2012

• Overview Fractures and vitamin D

• Seniors need at least 4,000 IU vitamin D, no test needed – Consensus Jan 2014

• 137 health problems associated with low vitamin D – meta-meta-analysis April 2014

  • published after the study on this page

• Stress fractures in basic training associated with 2.5 ng less vitamin D – meta-analysis Nov 2014

  • published after the study on this page

• Save 2 billion dollars annually in fractures if take Vitamin D and Calcium – Frost and Sullivan Sept 2013

• Calcium supplements proven to NOT reduce fractures, but are proven to INCREASE heart problems – July 2015 Bolland is co-author

• All items in category Meta-analysis items

  Pages listed in BOTH the categories Falls/Fractures and Meta-analysis

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