Vitamin D and risk of cause specific death: systematic review and meta-analysis of observational cohort and randomised intervention studies
What this study found
Overall vitamin D supplementation did not significantly reduce all-cause mortality across all trials, with a pooled risk ratio of 0.98 (0.94 to 1.02). In subgroup analyses, vitamin D3 was associated with lower all-cause mortality, RR 0.89 (0.80 to 0.99), whereas vitamin D2 showed no benefit, RR 1.04 (0.97 to 1.11). The intervention arm recorded 2527 all-cause deaths versus 2587 in control across the pooled trials. The review concluded that vitamin D3 may reduce mortality in older adults, but the overall evidence does not support a clear mortality benefit for vitamin D supplementation as a…
- Study & population
- Systematic review and meta-analysis of observational cohort studies and randomized intervention trials assessing mortality outcomes related to circulating 25-hydroxyvitamin D and vitamin D supplementation.
- Intervention
- In the randomized trials, vitamin D was given orally as tablets, mainly as daily vitamin D3 (cholecalciferol) at 10 to 6000 IU/day or daily vitamin D2 (ergocalciferol) at 208 to 4500 IU/day.
- Key limitation
- The randomized evidence was heterogeneous in vitamin D form, dose, duration, and trial quality, which limits direct comparison and makes the pooled estimate less definitive.
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Open PDFOriginal abstract
Objective To evaluate the extent to which circulating biomarker and supplements of vitamin D are associated with mortality from cardiovascular, cancer, or other conditions, under various circumstances. Design Systematic review and meta-analysis of observational studies and randomised controlled trials. Data sources Medline, Embase, Cochrane Library, and reference lists of relevant studies to August 2013; correspondance with investigators. Study selection Observational cohort studies and randomised controlled trials in adults, which reported associations between vitamin D (measured as circulating 25-hydroxyvitamin D concentration or vitamin D supplement given singly) and cause specific mortality outcomes. Data extraction Data were extracted by two independent investigators, and a consensus was reached with involvement of a third. Study specific relative risks from 73 cohort studies (849 412 participants) and 22 randomised controlled trials (vitamin D given alone versus placebo or no treatment; 30 716 participants) were meta-analysed using random effects models and were grouped by study and population characteristics. Results In the primary prevention observational studies, comparing bottom versus top thirds of baseline circulating 25-hydroxyvitamin D distribution, pooled relative risks were 1.35 (95% confidence interval 1.13 to 1.61) for death from cardiovascular disease, 1.14 (1.01 to 1.29) for death from cancer, 1.30 (1.07 to 1.59) for non-vascular, non-cancer death, and 1.35 (1.22 to 1.49) for all cause mortality. Subgroup analyses in the observational studies indicated that risk of mortality was significantly higher in studies with lower baseline use of vitamin D supplements. In randomised controlled trials, relative risks for all cause mortality were 0.89 (0.80 to 0.99) for vitamin D3 supplementation and 1.04 (0.97 to 1.11) for vitamin D2 supplementation. The effects observed for vitamin D3 supplementation remained unchanged when grouped by various characteristics. However, for vitamin D2 supplementation, increased risks of mortality were observed in studies with lower intervention doses and shorter average intervention periods. Conclusions Evidence from observational studies indicates inverse associations of circulating 25-hydroxyvitamin D with risks of death due to cardiovascular disease, cancer, and other causes. Supplementation with vitamin D3 significantly reduces overall mortality among older adults; however, before any widespread supplementation, further investigations will be required to establish the optimal dose and duration and whether vitamin D3 and D2 have different effects on mortality risk.