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Table 1 Basic characteristics of included articles reporting the association between vitamin D and COVID-19 infection and death, effect of vitamin D supplement on clinical outcomes in patients with COVID-19

From: Low vitamin D levels do not aggravate COVID-19 risk or death, and vitamin D supplementation does not improve outcomes in hospitalized patients with COVID-19: a meta-analysis and GRADE assessment of cohort studies and RCTs

Author, publication year, country Study design, Follow up Source of patients Sample size (N) Mean age (years), male Definition of Vitamin D exposure Expose level of vitamin D OR (95% CI)a Adjustments for confounders
Hastie, 2020, UK [6, 8] Prospective cohort study UK Biobank 341,484 49, 48% Conducted between 2006 and 2010 Per 10 ng/ml
< 20 ng/ml
> 20 ng/ml
Per 10 nmol/L
< 20 ng/ml
> 20 ng/ml
COVID-19 infection
1.00 (0.89–1.12)
1.06 (0.89–1.26)
Ref
Death
0.95 (0.79–1.15)
1.02 (0.75–1.38)
Ref
Age, sex, ethnicity, month of assessment, Townsend deprivation quintile, household income, BMI category, smoking status, diabetes, systolic blood pressure, diastolic blood pressure, self-reported health rating, and long-standing illness, disability or infirmity
Hastie, 2020, UK [6, 8] Retrospective cohort study University of Chicago Medicine 498 49,25% Within 1 year before their first COVID-19 tests < 20 ng/ml
> 20 ng/ml
COVID-19 infection
1.77 (1.12–2.81)
Ref
Age, sex, ethnicity, race, employee status. Hypertension, DM, chronic pulmonary disease, pulmonary circulation disorders, depression, CKD, liver disease, comorbidities with immunosuppression, BMI
Radujkovic,2020, Germany [5] Retrospective cohort study Medical university Hospital of Heidelberg 185 60,51% At the time of admission and SARS-CoV-2 testing < 20 ng/ml
> 20 ng/ml
Death
11.27 (1.48–85.55)
Ref
Age, gender, and any comorbidities
Charoenngam,2021, US [14] Retrospective cohort study Boston University Medical Center 287 62,47% Measured at within 48 h after admission < 30 ng/ml
> 30 ng/ml
Death
Ref
0.62 (0.28–1.41)
Age, sex, BMI, insurance, race, smoking, alcohol drinking, type 2 DM, hypertension, dyslipidemia, CAD, cerebrovascular disease, COPD, asthma, CKD, ESRD,
malignancy, HIV infection, and heart failure.
Carpagnano, 2020, Italy [13] Retrospective cohort study Hospital Policlinic of Bari 42 NA At admission < 10 ng/ml
> 10 ng/ml
Death
5.68 (1.14–28.97)
Ref
Age, higher levels of creatinine, troponin, and IL-6
Katz D,2020, US [18] Retrospective cohort study UF health centers 887 NA, NA October 1, 2015, through June, 30, 2020, for vitamin D deficiency < 20 ng/ml
> 20 ng/ml
COVID-19 infection
2.27 (1.79–2.87)
Ref
Age, sex, malabsorption, PA, dental diseases, race, periodontal disease status, DM, obesity
Kaufman, 2020, US [19] Retrospective cohort study National clinical laboratory 191,779 54, 22% Most recent vitamin D level Per 10 ng/ml COVID-19 infection
0.85 (0.84–0.86)
Male, northern and central latitudes, predominately black non-Hispanic zip codes, and predominately Hispanic zip codes
Angelidi,2020, US [22] Retrospective cohort study 2 tertiary academic medical centers 144 66, 64% Hospital personnel at Regular intervals < 30 ng/ml
> 30 ng/ml
Per 10 ng/ml
Death
8.33 (1.6–50)
Ref
0.54(0.35–0.82)
Age, BMI, ARB or ACEI, in-hospital drug treatment, CRP, smoking, heart failure, CAD, diabetes, hypertension, C-reactive protein level, and corticosteroids
De Smet,2021, Germany [15] Retrospective cohort study AZ Delta General Hospital 186 69,58% Measured in patients with COVID-19 on admission and within 24 h < 20 ng/ml
> 20 ng/ml
Death
3.87(1.30–11.55)
Ref
Age, higher CT severity score, presence of chronic lung
AlSafar, 2021, Australia [12] Retrospective cohort study Abu Dhabi, or Rashed hospital in Dubai. 464 46.6,80% At recruitment < 20 ng/ml
> 20 ng/ml
Death
1.71 (0.66, 4.43)
Ref
Age, sex, and comorbidities, BMI
Karahan, 2021, Turkey [17] Retrospective cohort study Health Sciences University 149 64, 54% NA Per 10 ng/ml Death
0.93(0.88–0.98)
Age, smoking, hyperlipidemia,
DM, CKD, Chronic AF, congestive heart failure, acute kidney injury, CRP, lymphocyte count, white blood cell count, serum albumin
Author, publication year, country Design Sample size (male%); mean age(years) Number of participants in intervention and control groups 25(OH)D assay Mean baseline 25(OH)D concentrations, nmol/L (SD) Oral dose of vitamin D in the intervention group Control group Outcome
Murai,2021, US [20] Multicenter double-blind RCT 240(56),56.3 intervention = 120;
control = 120
NA 21.0 (10.2)
20.6 (8.1)
Single dose of 200,000 IU Placebo Death
Admission to ICU
Castillo,2020, Spain [16] Signal center RCT 76(59%),53.0 intervention = 50;
control = 26
NA NA Single dose of oral calcifediol (0.532 mg) Without Calcifediol treatment Death
Admission to ICU
  1. OR odd ratio, UCLA University of California Los Angeles, UK United Kingdom, US Unite Status, SES residential socioeconomic status, CKD chronic kidney diseases, ICU intensive care unit, AF atrial fibrillation, BMI body mass index, ARB Angiotensin Receptor Blocker, ACEI angiotensin converting enzyme inhibitors, CRP C-reactive protein, DM diabetes mellitus, CAD coronary heart disease, NA not available, RCT randomized controlled trial, ESRD end-stage renal disease, HIV human immunodeficiency virus
  2. aHazard ratio and incidence rate ratio were treated as odd ratio