Retrospective phone survey of 1,486 Parkinson's disease patients in Italy, showing lower risk of COVID-19 cases with vitamin D supplementation. This paper also presents a case control study of PD patients and family member control patients.
Fasano et al., 6/2/2021, retrospective, Italy, Europe, peer-reviewed, 7 authors, dosage not specified.
risk of COVID-19 case, 42.0% lower, RR 0.58, p = 0.05, treatment 13 of 329 (4.0%), control 92 of 1157 (8.0%), odds ratio converted to relative risk.
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.