Table 1

Characteristics of trials and participants included in individual participant data meta-analysis

Study first author and yearSettingMean age, years (SD) [range]Male:femaleGOLD spirometric grade, N (%)Ethnic origin25(OH)D assayMean baseline 25(OH)D, nmol/L (SD) [range]Baseline 25(OH)D <25 nmol/L (%)Intervention:
control, all participants (participants with baseline 25(OH)D <25 nmol/L)
Oral dose of vitamin D3, intervention armStudy durationN with available outcome data/N randomised (%)
Lehouck 201213 Secondary care, Belgium67.9 (8.3) [48–86]145:371: 2/182 (1.1).
2: 47/182 (25.8).
3: 91/182 (50.0).
4: 42/182 (23.1).
182/182 (100.0%) white European.RIA49.8 (29.2) [9.0–159.7]31/182 (17.0)91:91 (15:16)2.5 mg (100 000 IU) bolus monthly*12 months182/182 (100.0)
Martineau 201514 Primary and secondary care, UK64.7 (8.5) [40–85]144:961: 61/240 (25.4).
2: 113/240 (47.1).
3: 52/240 (21.7).
4: 14/240 (5.8).
227/240 (94.6%) white European†LC-MS/MS46.1 (25.7) [undetectable −160.0]50/240 (20.8)122:118 (29:21)3 mg (120 000 IU) bolus once every 2 months‡12 months240/240 (100.0)
Rafiq 201715 Secondary care, Netherlands62.5 (5.6) [48–71]26:241: 10/50 (20.0).
2: 22/50 (44.0).
3: 13/50 (26.0).
4: 5/50 (10.0).
49/50 (98.0%) white European§LC-MS/MS41.4 (16.0) [17.0–90.0]6/50 (12.0)24:26 (4:2)30 µg (1200 IU) daily6 months47/50 (94.0)
  • GOLD grade 1: FEV1 ≥80% predicted; grade 2, FEV1 50.0%–79.9% predicted; grade 3, FEV1 30.0%–49.9% predicted; grade 4, FEV1 <30.0% predicted. 40 international units (IU) vitamin D3 = 1 µg; 25(OH)D concentrations reported in ng/ml were converted to nmol/L by multiplying by 2.496.

  • *Approximately equivalent to a daily dose of 83 µg (3320 IU) vitamin D3.

  • †Other participants classified ethnic origin as black African (n=1), Caribbean (n=1), Filipino (n=1), Indian (n=1), Pakistani (n=2), mixed white and Asian (n=1), mixed white and black African (n=1), mixed white and black Caribbean (n=2), Mauritian (n=1) and other (n=2).

  • ‡Approximately equivalent to a daily dose of 50 µg (2000 IU) vitamin D3.

  • §Other participant classified ethic origin as Indian.

  • 25(OH)D, 25-hydroxyvitamin D; mo, month; yr, year; wk, week. DEQAS, Vitamin D External Quality Assessment Scheme; LC-MS/MS, liquid chromatography tandem-mass spectrometry, RIA, radio-immunoassay.