Case control study in China comparing 62 patients with 80 healthy controls showing vitamin D deficiency is a risk factor for COVID-19, especially for severe/critical cases.
Ye et al., 10/13/2020, retrospective, China, Asia, peer-reviewed, 18 authors.
risk of severe/critical COVID-19, 93.4% lower, RR 0.07, p = 0.03, high D levels 2 of 36 (5.6%), low D levels 8 of 26 (30.8%), adjusted per study, >50nmol/L.
Effect extraction follows pre-specified rules prioritizing more serious
outcomes. For an individual study the most serious outcome may have a smaller
number of events and lower statistical signficance, however this provides the
strongest evidence for the most serious outcomes when combining the results of
many trials.