From:  Bidirectional relationship between vitamin D deficiency and type 1/type 2 diabetes mellitus: a systematic review and meta-analysis

 Subgroup analyses

SubgroupEffects of VDD on the risk of T2DMEffects of T1DM on the risk of VDDEffects of T2DM on the risk of VDD
StudyOR (95% CI)P valueI2Egger’s testGRADEStudyOR (95% CI)P valueI2Egger’s testGRADEStudyOR (95% CI)P valueI2Egger’s testGRADE
Total51.53 [1.38–1.70]< 0.0000166%0.109Very low232.02 [1.42–2.89]0.000181%0.055Low272.62 [1.85–3.70]< 0.0000190%0.038Low
Study design
Prospective51.53 [1.38–1.70]< 0.0000166%0.109Very lowNANANANANANA11.64 [1.25–2.14]0.0003NANAVery low
RetrospectiveNANANANANANA232.02 [1.42–2.89]0.000181%0.055Low262.71 [1.86–3.95]< 0.0000190%0.038Low
Follow-up
≥ 5 years31.66 [1.60–1.71]< 0.000010%NALowNANANANANANA11.64 [1.25–2.14]0.0003NANAVery low
< 5 years21.34 [0.95–1.88]0.0984%NAVery lowNANANANANANANANANANANANA
Region
Asia11.56 [1.43–1.70]< 0.00001NANAVery low152.21 [1.55–3.15]< 0.000174%0.165Low232.38 [1.67–3.39]< 0.0000190%0.049Low
Europe41.45 [1.17–1.78]0.000571%NAVery low21.65 [1.03–2.64]0.040%NAVery lowNANANANANANA
North AmericaNANANANANANA21.67 [0.83–3.37]0.150%NAVery lowNANANANANANA
AfricaNANANANANANA33.71 [0.26–53.46]0.3396%NAVery low34.75 [0.55–41.06]0.1692%NAVery low
AustraliaNANANANANANA11.73 [0.39–7.62]0.47NANAVery lowNANANANANANA
South AmericaNANANANANANANANANANANANA111.50 [4.76–27.75]< 0.00001NANALow
Sample size
≥ 1,00041.54 [1.38–1.71]< 0.0000173%NALowNANANANANANA42.44 [1.74–3.42]< 0.0000179%NALow
< 1,00011.24 [0.65–2.38]0.51NANAVery low232.02 [1.42–2.89]0.000181%0.055Low232.80 [1.73–4.53]< 0.000191%0.024Low
Mean/median age
≥ 50 years21.38 [0.92–2.06]0.1290%NAVery lowNANANANANANA123.29 [2.02–5.34]< 0.0000186%0.111Low
< 50 yearsNANANANANANA232.02 [1.42–2.89]0.000181%0.055Low112.87 [1.53–5.37]0.00190%0.014Very low
Mean/median BMI
≥ 30 kg/m2NANANANANANANANANANANANA25.21 [0.08–332.64]0.4488%NAVery low
≥ 25, < 30 kg/m221.38 [0.92–2.06]0.1290%NAVery low21.67 [0.83–3.37]0.150%NAVery low91.30 [0.71–2.37]0.492%NAVery low
≥ 18.5, < 25 kg/m2NANANANANANA41.23 [0.32–4.63]0.7690%NAVery low27.68 [3.94–14.95]< 0.000010%NAModerate
< 18.5 kg/m2NANANANANANA92.91 [1.71–4.94]< 0.000167%NALow140.38 [5.08–320.74]0.0005NANALow
Assay method
CLIA31.65 [1.60–1.70]< 0.000010%NALow71.98 [1.02–3.83]0.0480%NAVery low31.83 [0.86–3.90]0.1274%NAVery low
RIA21.12 [0.88–1.42]0.370%NAVery low32.61 [1.86–3.68]< 0.000010%NAModerate27.79 [0.43–141.44]0.1687%NAVery low
ELISANANANANANANA62.18 [0.72–6.55]0.1792%NAVery low122.64 [1.50–4.64]0.000890%0.004Low
HPLCNANANANANANA41.94 [0.87–4.34]0.1163%NAVery low42.91 [1.38–6.11]0.00577%NAVery low
LC-MS/MSNANANANANANA12.04 [1.31–3.15]0.001NANAVery lowNANANANANANA
Latitude climate zone
Temperate zone51.53 [1.38–1.70]< 0.0000166%0.109Very low191.94 [1.35–2.80]0.000481%0.055Very low172.54 [1.59–4.05]< 0.000192%0.038Low
Tropical zoneNANANANANANA42.55 [0.56–11.61]0.2383%NAVery low102.89 [1.69–4.94]0.000183%0.147Low
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BMI: body mass index; CI: confidence interval; CLIA: chemiluminescence immunoassay; ELISA: enzyme-linked immunosorbent assay; GRADE: Grading of Recommendations, Assessment, Development, and Evaluation; HPLC: high performance liquid chromatography; LC-MS/MS: Liquid chromatography-tandem mass spectrometry; NA: not available; ORs: odds ratios; RIA: radioimmunoassay; T1DM: type 1 diabetes mellitus; T2DM: type 2 diabetes mellitus; VDD: vitamin D deficiency