medwireNews: Results from a series of case–control studies involving over 135,000 participants have failed to show any benefit of vitamin D supplementation in the prevention of pneumonia.
Furthermore, the findings raise the possibility that there are some groups of patients for whom supplementation may actually confer an increased risk for the condition.
The analysis included three independent case–control studies: ANTONIUS-PHARMO involved 504 patients with confirmed community-acquired pneumonia and 2016 matched controls; PHARMO-PHARMO included 20,824 patients with pneumonia and 41,268 matched controls; and NPCRD-NPCRD included 12,398 general practitioner-diagnosed pneumonia cases and 61,959 matched controls.
The authors, led by Hilde Remmelts (University Medical Center Utrecht, the Netherlands), found that, in crude analysis, vitamin D supplementation was associated with an elevated risk for pneumonia. But after adjusting for confounders, such as presence of asthma and corticosteroid use, this only remained significant in the NPCRD-NPCRD cohort, in which supplement users had a 50% greater odds for pneumonia than did non-users.
Interestingly, the researchers identified osteoporosis, defined by the use of bisphosphonates and/or calcium, and oral corticosteroid use as significant effect modifiers, each in two of the case–control studies, suggesting that the risk for pneumonia was increased in patients taking vitamin D without drugs that affect bone mineralization.
“This might indicate unmeasured confounding, insufficient supplementation or a true risk,” the authors comment, adding that further research will be needed to explore this association.
Writing in Thorax, Remmelts and team say that the findings were contrary to their expectations, as previous research into the associations between vitamin D supplementation and respiratory tract infection in children have found positive results. However, noting the age of their cohorts (all means >60 years), the authors comment:“this suggests that any preventive effects, if present, do not extend to older people, in whom there is considerable prevalence of vitamin D deficiency.”
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