TABLE 1.
Characteristics of studies investigated association of vitamin D status with SARS-CoV-2 infection1
| First author (ref) | Study date | Country, setting | Design | Sample size, n | Age (y); sex | Definition of VitD deficiency | Time of VitD ascertainment | Objective/study question | Adjusting factors |
|---|---|---|---|---|---|---|---|---|---|
| Bahat (31) | April and June, 2020 | A tertiary referral hospital, Turkey | Descriptive | 44 SARS-CoV-2-positive (+) pregnant women who were hospitalized, >8 wk of gestation | Mean age: 28.57; female: 100% | Serum 25(OH)D <20 ng/mL | On the day of admission | To measure serum 25(OH)D concentration in SARS-CoV-2+ pregnant women | — |
| Baktash (47) | March 1 and April, 2020 | General hospital in the UK | Prospective cohort | 105 elderly (>65 y) participants, 70 SARS-CoV-2+, 35 SARS-CoV-2 negative (–) | Mean age: 81.28; patients: 60% male; healthy: 40% | Serum 25(OH)D ≤12 ng/mL | Concurrent with SARS-CoV-2 test | Relation between VDD and SARS-CoV-2 infection | No adjustment for confounders; another limitation is vitamin D intake after the acute phase of illness |
| Blanch-Rubió (37) | March 1 to May 3, 2020 | Rheumatology service of hospital, Spain | Cross-sectional | 2102 patients with noninflammatory rheumatic conditions | Mean age: 66.4; 80.5% female | — | — | Effect of vitamin D intake on COVID-19 incidence | Sex, age, comorbidities, treatment, and drugs |
| D'Avolio (48) | March 1 to April 14, 2020 | Switzerland | Retrospective cohort | 27 SARS-CoV-2+, 80 SARS-CoV-2– | Median age: 73, IQR (63 to 81); male: 54.2% | — | The vitamin D analysis was required to be conducted within 7 wk of the SARS-CoV-2 PCR result | Describing the 25(OH)D plasma concentrations in a cohort of patients from Switzerland | — |
| De Smet (42) | March 16 to April 16, 2020 | General hospital in Belgium | Retrospective observational study | 186 SARS-CoV-2+ hospitalized patients and 2717 diseased controls | Patients: median age, (IQR): 69 (52–80); male: 58.6%; controls: 68 (49–82); male: 36.8% | Serum 25(OH)D <20 ng/mL | Measured after SARS-CoV-2 test | Are lower 25(OH)D concentrations correlated with COVID-19? | — |
| Ferrari (43) | February to April, 2020 | The San Raffaele Hospital, Milan, Italy | Retrospective cohort | 128 SARS-CoV-2+, 219 SARS-CoV-2– | Patients: 64.8% males; male age: 62.7; female age: 69.3; healthy: 48.85% males; male age: 62.8, female age: 54.3 | Serum 25(OH)D ≤30 ng/mL | The average time interval between SARS-CoV-2 test and their corresponding 25(OH)D measurements for the positive group was 33.9 and for the negative group was 33.33 d | — | — |
| Hernández (44) | March 10 to March 31, 2020 | University Hospital, Spain | Retrospective case-control study | 216 SARS-CoV-2+ and 197 population-based controls; in COVID-19 patients: number of VDD: 35; number of non-VDD: 162 | Cases: age, median (IQR): 61.0 (47.5–70.0); controls: 61.0 (56.0–66.0); male: 62.4% in both groups | Serum 25(OH)D <20 ng/mL | At admission | To assess serum 25(OH)D concentrations in hospitalized patients with COVID-19 and to analyze the possible influence of vitamin D status on disease severity | — |
| Im (45) | February to June, 2020 | Inha University Hospital, South Korea | Case-control | 50 patients with SARS-CoV-2+ and 150 controls | Mean age: 57.5 in case and 52.2 in control groups; male: 58% | Serum 25(OH)D3 <20 ng/mL | Within 7 d of admis?sion | Prevalence of VDD among COVID-19 patients, comparing vitamin D status between COVID-19 patients and healthy individuals | Control group was matched for age and sex with the COVID-19 group |
| Kerget (50) | March 24, to May 15, 2020 | University Hospital in Turkey | Case-control | 88 SARS-CoV-2+, 20 SARS-CoV-2– | Mean age:cases: 49.1;male: 60%; controls: 35.2; male: 40% | — | Fifth day of admission to hospital | To determine the relation of serum vitamin D concentration between patients and healthy controls | — |
| Luo (46) | February 27 to March 21, 2020 | Hospital in China | Cross-sectional | 335 COVID-19 patients, age- and sex-matched population of 560 individuals | Patients: median (IQR) age: 56 (43–64);male: 44.2%; controls: age: 55 (49.0–60.0);male: 45.9% | Serum 25(OH)D <30 ng/mL | In control, serum 25(OH)D concentrations were measured during the same period from 2018–2019; in patients, serum 25(OH)D concentrations were measured on admission | To investigate whether VDD is associated with COVID-19 incidence | Age, sex, comorbidities, smoking status, and BMI |
| Mardani (49) | March, 2020 | A general clinic, Iran | Case-control | 63 SARS-CoV-2+, 60 SARS-CoV-2– | Median age of 39; male: 52% | Deficient [25(OH)D <10 ng/mL], insufficient [25(OH)D: 10–30 ng/mL] | At baseline of the study | Relation between VDD and SARS-CoV-2 infection | Not adjusted |
| Meltzer (39) | March 3 to April 10, 2020 | Academic hospital in USA | Retrospective cohort study | 63 SARS-CoV-2+, 365 SARS-CoV-2– | Mean age: 45.7; male: 25.2% | VDD was defined by the most recent 25(OH)D <20 ng/mL or 1,25(OH)D<18 pg/mL | Within 1 y before SARS-CoV-2 test (subjects received treatment in this duration were excluded) | Is VDD associated with positive test for SARS-CoV-2? | Demographic and comorbidity |
| Merzon (40) | February 1 to March 30, 2020 | Health Services in Israel | Retrospective cohort study | 782 SARS-CoV-2+, 7025 SARS-CoV-2– | SARS-CoV-2+: mean age: 35.6; male: 49.23%;SARS-CoV-2–: mean age: 47.4; male: 40.6% | “Suboptimal” or “low”: plasma 25(OH)D <30 ng/mL | At least 1 previous blood test for plasma 25(OH)D concentration | Is VDD risk factor for SARS-CoV-2 infection? | Demographic variables, psychiatric and somatic disorders |
| Sun (34) | February to February, 2020 | Hospital University in Wuhan, China | Descriptive | 241 patients with confirmed COVID-19 | Median age: 65 (IQR: 55–72); male: 46.4% | — | Within 24 h of admission | 25(OH)D concentration in SARS-CoV-2+ adults | — |
| Ye (41) | February to March, 2020 | A Hospital in China | Case-control | 62 SARS-CoV-2+, 80 healthy controls | Controls: median age (IQR): 42 (31–52); male: 40%; patients: age: 43 (32–59); male: 37% | 25(OH)D <20 ng/mL | At admission | To examine the relation between serum 25(OH)D concentration and SARS-CoV-2 infection | Demographics and comorbidities |
| Yılmaz (35) | March to May, 2020 | University Hospital in Turkey | Case-control | 85 children (40 SARS-CoV-2+ and hospitalized, 45 healthy children in control group) | COVID-19 patients: 101.76 mo; male: 47.5%; controls: 75.68 mo; male: 60% | 25(OH)D <12 ng/mL | From retrospective file records | Is VDD a risk factor for COVID-19 in children? | None |
1COVID-19, coronavirus disease 2019; PCR, polymerase chain reaction; ref, reference; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; VDD, vitamin D deficiency; VitD, vitamin D; 25(OH)D, 25-hydroxyvitamin D; 25(OH)D3, 25-hydroxyvitamin D3; 1,25(OH)D, 1,25-hydroxyvitamin D.