Correlation between premorbid IL-6 levels and COVID-19 mortality: Potential role for Vitamin D

There is recent evidence that interleukin-6 (IL-6) levels are elevated in cases of complicated COVID-19, but it is also possible that this cytokine may have a far more important role in the pathogenesis of viral infection. IL-6 is known to be modulated by Vitamin D, and there is preliminary evidence that deficiency of this vitamin is linked to poorer outcomes. To identify whether IL-6 levels prior to infection might predict outcome, early data on COVID-19 mortality from Italy and the UK were compared with previously published results of mean IL-6 levels from these countries as well as from the USA. There was a highly significant correlation (r = 0.9883; p = 0.00025) between age-stratified mortality rates and IL-6 levels from previously published data on healthy individuals. To determine whether Vitamin D may be beneficial at lowering IL-6 levels in patients, a limited analysis of trials examining the relationship between these entities published since 2015 was undertaken. Eight out of 11 studies described a significant lowering effect of Vitamin D on IL-6. Given that IL-6 likely facilitates viral cell entry and replication, levels prior to infection may predict mortality. This provides a rationale for prophylactic and therapeutic measures directed at lowering IL-6, including Vitamin D prescription.