Vitamin D and Pneumonia- Mortality levels impacted- from Medscape
Posted May 17 2011 8:30pm
Emma Hitt, PhD
May 11, 2011 — A prospective study in patients with community-acquired pneumonia indicates an increased 30-day mortality in patients with severe 25-hydroxyvitamin D deficiency compared with those patients with sufficient vitamin D levels.
Leong Leow, MD, from the Waikato Hospital in Hamilton, New Zealand, and colleagues reported their findings in the May issue of Respirology.
The authors hypothesize that because of the known antimicrobial effects of vitamin D, blood levels of 25-hydroxyvitamin D might be related to disease severity and outcomes in hospitalized patients with community-acquired pneumonia.
Severe 25-hydroxyvitamin D deficiency, defined as a blood level lower than 30 nmol/L, was found in 15% of patients in the study cohort. Patients with severe 25-hydroxyvitamin D deficiency had a significantly greater mortality (odds ratio, 12.7; 95% con?dence interval, 2.2 - 73.3; P = .004) compared with those with sufficient 25-hydroxyvitamin D levels (>50 nmol/L).
According to the researchers, increased mortality was observed only in patients with severe 25-hydroxyvitamin D deficiency, indicating that the relationship between blood levels and mortality appears to be nonlinear. In addition, the increase in mortality was not accounted for by comorbidities, differences in age, or severity of acute illness.
Blood concentrations of 25-hydroxyvitamin D were not associated with the Charlson comorbidity index, other indexes of frailty, or the fact that a patient was in residential care.
The researchers speculate that given that the main source of vitamin D for most people is sunlight exposure, deprivation of sunlight during the winter months might plausibly contribute to the increased prevalence of pneumonia during this time.
In addition, as vitamin D is known to regulate the synthesis of the antimicrobial peptides cathelicidin and beta-defensin-2, the authors hypothesized that serum levels of both molecules should be associated with vitamin D concentrations, as well as 30-day mortality. However, the study did not find an association between the blood levels of cathelicidin and beta-defensin-2 and that of 25-hydroxyvitamin D.
Furthermore, there was no significant association between cathelicidin and beta-defensin-2 blood levels and mortality, although a trend toward increased mortality was found with lower blood levels of cathelicidin (P = .053).
The authors point out several study limitations. First, an observational study cannot demonstrate a causal relationship between 25-hydroxyvitamin D levels and mortality, and it is possible that the 25-hydroxyvitamin D blood level is a biomarker for frailty and poor prognosis. Second, the findings cannot be generalized to nonhospitalized patients with pneumonia who are treated in the community.
"These observations raise the possibility that vitamin D supplements and cathelicidin could have a therapeutic role in acute infections," Dr. Leow and colleagues conclude.
The study funded by a grant from the Waikato Medical Research Foundation.