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New meta-analysis adds clarity to the role of vitamin D in hospital mortality

Posted on: January 2, 2015   by  Amber Tovey


A recent meta-analysis of over 4,000 participants found that vitamin D deficiency is associated with increased incidence of hospital mortality among critically ill adults.

Research has provided a large amount of evidence that indicates vitamin D deficiency is related to adverse health outcomes in critically ill patients, such as higher infection rates, prolonged length of stay, and hospital mortality.

However, a few studies from this past year have raised concerns regarding these findings. One cohort of 180 critically ill patients found no association between low vitamin D levels and increased mortality rates. This study suggested that those with vitamin D levels above 100 ng/ml experienced significantly higher mortality rates when compared to the other participants.

In June, Will Hunter covered a cohort study in which researchers found a u-shaped relationship between pre-hospital vitamin D status and mortality.

Given this conflicting evidence, researchers from China recently conducted a large meta-analysis to help clear up the conflicting research.

The researchers included seven cohort studies, three retrospective and four prospective cohorts, equaling a total of 4,204 participants into their meta-analysis. All cohorts focused on the relationship between vitamin D status and hospital or ICU mortality.

After analyzing the data, here is what they found:

  • Vitamin D deficiency was significantly associated with increased hospital mortality (p < 0.001).
  • Patients who were vitamin D deficient were 76% more likely to die in the hospital.
  • All studies defined vitamin D deficiency differently, but stratifying participants based on specific vitamin D levels yielded similar results.

The researchers concluded,

“This study showed that vitamin D deficiency is associated with an increased hospital mortality in critically ill adult patients. However, there is not enough evidence to conclude that vitamin D deficiency is associated with increased ICU mortality in critically ill adult patients, which need more studies to probe further into it in the future.”

They went on to add,

“Vitamin D levels may not only predict disease severity and outcomes but also contribute to the co-morbidities commonly seen in critically illness.”

They pointed out that some studies were conducted in specific ICUs, such as a surgical ICU, which limits the study’s generalizability to all hospital patients. Also, the cohorts defined vitamin D deficiency differently which could affect the study’s primary findings.

It is unlikely that clinical trials comparing vitamin D to a placebo group of critically ill patients will ever be conducted due to ethical objections. Future studies should find the safest and most effective dose of vitamin D for critically ill patients.


Zhang Y. et al. Association between vitamin D deficiency and mortality in critically ill adult patients: a meta-analysis of cohort studies. Critical care, 2014.

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