Low plasma vitamin D levels emerged as an independent risk factor for COVID-19 infection and hospitalization in a large, population-based study.
Participants positive for COVID-19 were 50% more likely to have low vs normal 25(OH)D levels in a multivariate analysis that controlled for other confounders, for example.
The take home message for physicians is to “test patients’ vitamin D levels and keep them optimal for the overall health – as well as for a better immunoresponse to COVID-19,” senior author Milana Frenkel-Morgenstern, PhD, head of the Cancer Genomics and BioComputing of Complex Diseases Lab at Bar-Ilan University in Ramat Gan, Israel, said in an interview.
The study was published online July 23 in The FEBS Journal.
Previous and ongoing studies are evaluating a potential role for vitamin D to prevent or minimize the severity of SARS-CoV-2 infection, building on years of research addressing vitamin D for other viral respiratory infections. The evidence to date regarding COVID-19, primarily observational studies, has yielded mixed results.
Multiple experts weighed in on the controversy in a previous report. Many point out the limitations of observational data, particularly when it comes to ruling out other factors that could affect the severity of COVID-19 infection. In addition, in a video report, JoAnn E. Manson, MD, DrPH, of Harvard Medical School in Boston, cited an observational study from three South Asian hospitals that found more severe COVID-19 patients had lower vitamin D levels, as well as other “compelling evidence” suggesting an association.
Dr. Frenkel-Morgenstern and colleagues studied data for 7,807 people, of whom 10.1% were COVID-19 positive. They assessed electronic health records for demographics, potential confounders, and outcomes between February 1 and April 30.
Participants positive for COVID-19 tended to be younger and were more likely to be men and live in a lower socioeconomic area, compared with the participants who were negative for COVID-19, in a univariate analysis.
A higher proportion of COVID-19–positive patients had low plasma 25(OH)D concentrations, about 90% versus 85% of participants who were negative for COVID-19. The difference was statistically significant (P < .001). Furthermore, the increased likelihood for low vitamin D levels among those positive for COVID-19 held in a multivariate analysis that controlled for demographics and psychiatric and somatic disorders (adjusted odds ratio, 1.50). The difference remained statistically significant (P < .001).
The study also was noteworthy for what it did not find among participants with COVID-19. For example, the prevalence of dementia, cardiovascular disease, chronic lung disorders, and hypertension were significantly higher among the COVID-19 negative participants.
“Severe social contacts restrictions that were imposed on all the population and were even more emphasized in this highly vulnerable population” could explain these findings, the researchers noted.
“We assume that following the Israeli Ministry of Health instructions, patients with chronic medical conditions significantly reduced their social contacts” and thereby reduced their infection risk.
In contrast to previous reports, obesity was not a significant factor associated with increased likelihood for COVID-19 infection or hospitalization in the current study.
The researchers also linked low plasma 25(OH)D level to an increased likelihood of hospitalization for COVID-19 infection (crude OR, 2.09; P < .05).
After controlling for demographics and chronic disorders, the aOR decreased to 1.95 (P = .061) in a multivariate analysis. The only factor that remained statistically significant for hospitalization was age over 50 years (aOR, 2.71; P < .001).