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
665 items 25 Pages listed in BOTH the categories Falls/Fractures and Meta-analysis - No increase in falls, fractures or all-cause mortality when Vitamin D is given monthly or less often– meta-analysis April 2024
- 100,000 IU of Vitamin D monthly (27 ng) is not enough to reduce fractures and falls – meta-analysis April 2024
- Increased risk of fracture if high level of Vitamin D (if continue to take Calcium) – umbrella analysis of meta-analyses Nov 2020
- Hip fractures not prevented by Vitamin D (800 IU daily or large quarterly or annual doses) – meta-analysis – Dec 2019
- Vitamin K (any amount and any kind) reduced bone fractures by 24 percent – meta-analysis – May 2019
- Vitamin D not help fractures and falls if not vitamin D deficient – meta-analysis Oct 2018
- Fractures not reduced by small amounts of vitamin D - meta-analysis Dec 2017
- Preventing Falls in Older Adults – Vitamin D combination is the best - JAMA Meta-analysis Nov 2017
- Hip fracture 58 percent more likely if low vitamin D – meta-analysis March 2017
- Fracture risk reduced somewhat by 800 IU of vitamin D and Calcium – meta-analysis Oct 2015
- Acute fracture patients – 70 percent were vitamin D deficient – meta-analysis Sept 2015
- Falls not prevented by vitamin D given every 3 months or less often – meta-analysis Jan 2015
- Vitamin D prevents falls – majority of meta-analyses conclude – meta-meta analysis Feb 2015
- Vitamin D and fractures – 24 meta-analyses and counting – Dec 2014
- Bone fractures reduced by a minimum of 800 IU vitamin D and Calcium – meta-meta-analysis March 2014
- Fractures reduced with any amount of vitamin D and some Calcium - Cochraine April 2014
- Fallers often had less than 20 ng of vitamin D – meta-analysis April 2014
- Hip fractures greatly reduced by sunshine, vitamin D, and vitamin K – meta-analysis Sept 2012
- Vitamin D may prevent falls and fractures without Calcium – an overview of 9 meta-analysis – Oct 2012
- Hip fractures reduced 30 percent with 800 IU of vitamin D – meta-analysis July 2012
- Vitamin D reduces falls – meta-analysis Oct 2011
- Active form of vitamin D (calcitriol) cut in half the fractures following organ transplant – meta-analysis Aug 2011
- 1000 IU minimum to decrease falls and fractures Swiss - 2009
- Meta-analysis of falls and 800+ IU of vitamin D found good results – June 2010
- 800 IU vitamin D reduces falls - Dec 2009
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