Vitamin D Supplementation and Fractures in Adults: A Systematic Umbrella Review of Meta-Analyses of Controlled Trials
Bibliographic record
Abstract
CONTEXT: The growing number of systematic reviews/meta-analyses (SR/MAs) on vitamin D (± calcium) for fracture prevention has led to contradictory guidelines. OBJECTIVE: This umbrella review aims to assess the quality and explore the reasons for the discrepancy of SR/MAs of trials on vitamin D supplementation for fracture risk reduction in adults. METHODS: We searched 4 databases (2010-2020), Epistemonikos, and references of included SRs/MAs, and we contacted experts in the field. We used A MeaSurement Tool to Assess systematic Reviews 2 (AMSTAR-2) for quality assessment. We compared results and investigated reasons for discordance using matrices and subgroup analyses (PROSPERO registration: CRD42019129540). We included 13 SR/MAs on vitamin D and calcium (Ca/D) and 19 SR/MAs on vitamin D alone, compared to placebo/control. RESULTS: Only 2 from 10 SRs/MAs on Ca/D were of moderate quality. Ca/D reduced the risk of hip fractures in 8 of 12 SRs/MAs (relative risk [RR] 0.61-0.84), and any fractures in 7 of 11 SR/MAs (RR 0.74-0.95). No fracture risk reduction was noted in SRs/MAs exclusively evaluating community-dwelling individuals or in those on vitamin D alone compared to placebo/control. Discordance in results between SRs/MAs stems from inclusion of different trials, related to search periods and eligibility criteria, and varying methodology (using intention to treat, per-protocol, or complete case analysis from individual trials). CONCLUSION: Ca/D reduces the risk of hip and any fractures, possibly driven by findings from institutionalized individuals. Individual participant data meta-analyses of patients on Ca/D with sufficient follow-up periods, and subgroup analyses, would unravel determinants for a beneficial response to supplementation.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.039 | 0.143 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.053 | 0.008 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.002 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; both teacher heads agree on what is shown here.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".