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Table 2 Results of pairwise and dose–response meta-analysis

From: Optimal methods of vitamin D supplementation to prevent acute respiratory infections: a systematic review, dose–response and pairwise meta-analysis of randomized controlled trials

Group

Study number; Patient number

Dose–response meta-analysis, RR (95% CI)

Pairwise Meta-analysis, RR (95% CI), NNT

400 IU/d

800 IU/d

1200 IU/d

Main analysis

 All [28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70]

43; 49,320

0.99 (0.98–1.01)

0.99 (0.96–1.02)

0.99 (0.96–1.02)

0.99 (0.97–1.01)

Subgroup analysis

 Age group (years)

  < 7 [30, 32, 37, 39, 42, 51, 52, 54, 56, 60, 67, 69]

12; 8826

0.95 (0.87–1.03)

0.93 (0.83–1.04)

0.93 (0.84–1.03)

0.97 (0.91–1.13)

  7–17 [31, 33, 35, 44, 45, 55, 61, 64, 65]

9; 11,525

NA

NA

NA

1.00 (0.96–1.04)

  18–65 [28, 29, 34, 38, 40, 41, 46, 47, 49, 50, 57, 59, 70]

13; 3891

0.97 (0.91–1.03)

0.95 (0.86–1.05)

0.93 (0.84–1.04)

0.94 (0.86–1.02)

  > 65 [36, 43, 48, 53, 58, 62, 63, 66, 68]

9; 25,078

0.99 (0.97–1.01)

0.98 (0.95–1.01)

0.98 (0.94–1.01)

0.99 (0.98–1.01)

 Gender proportion (%)

  Male > 60 [29, 33, 36, 41, 44, 45, 51, 67]

8; 1930

0.92 (0.74–1.13)

0.93 (0.77–1.13)

0.95 (0.80–1.12)

0.96 (0.82–1.13)

  Male ≤ 60 [28, 30,31,32, 34, 35, 37,38,39,40, 42, 43, 46,47,48,49,50, 52,53,54,55,56,57,58,59,60,61,62,63,64,65,66, 68,69,70]

35; 47,390

0.99 (0.99–1.00)

0.99 (0.98–1.00)

0.99 (0.98–1.00)

0.99 (0.96–1.01)

 Comorbidity

  General [28, 29, 31, 35, 37, 38, 41,42,43,44,45, 48, 49, 52,53,54, 56,57,58, 60,61,62,63,64,65,66, 68,69,70]

29; 43,560

1.00 (0.99–1.01)

0.99 (0.98–1.01)

0.99 (0.98–1.01)

0.99 (0.97–1.01)

  Disease-specific [30, 32,33,34, 36, 39, 40, 46, 47, 50, 51, 55, 59, 67]

14; 5610

0.94 (0.88–1.01)

0.92 (0.83–1.01)

0.91 (0.81–1.02)

0.97 (0.91–1.03)

 Baseline 25-hydroxyvitamin D levels (nmol/L)

  < 50 [35, 36, 43, 46,47,48, 50, 54, 55, 57, 64, 70]

12; 11,588

0.99 (0.98–1.01)

0.99 (0.96–1.02)

0.99 (0.96–1.02)

0.98 (0.94–1.03)

  > 50 [28, 29, 33, 34, 38,39,40, 42, 45, 49, 52, 53, 56, 58,59,60,61,62,63, 65, 66]

21; 13,995

0.99 (0.98–1.01)

0.99 (0.96–1.02)

0.99 (0.96–1.02)

0.98 (0.95–1.02)

 Dosing frequency

  Bolus [30, 51, 67]

3; 1087

NA

NA

NA

0.96 (0.75–1.24)

  Daily [28, 29, 31, 33,34,35, 39, 40, 42, 44, 45, 50, 52, 54, 56,57,58,59,60, 62, 65, 69, 70]

23; 8788

0.94 (0.87–1.02)

0.92 (0.82–1.02)

0.92 (0.84–1.02)

0.92 (0.85–0.99), 36

  Weekly [32, 41, 49, 61, 64]

5; 12,864

NA

NA

NA

1.00 (0.98–1.02)

  Monthly [36,37,38, 43, 46,47,48, 53, 55, 63, 66, 68]

12; 26,581

0.99 (0.98–1.00)

0.99 (0.97–1.00)

0.98 (0.96–1.00)

1.00 (0.99–1.01)

 Trial duration (months)

  < 4 [28, 30, 35, 41, 44, 45, 57, 58, 69, 70]

10; 2845

0.86 (0.69–1.07)

0.80 (0.60–1.07)

0.81 (0.63–1.04)

0.81 (0.67–0.97), 16

  4–12 [29, 31,32,33, 39, 42, 49,50,51,52, 59,60,61, 65, 67]

15; 6698

0.92 (0.85–1.01)

0.91 (0.81–1.02)

0.93 (0.83–1.03)

0.97 (0.89–1.05)

  > 12 [34, 36,37,38, 40, 43, 46,47,48, 53,54,55,56, 62,63,64, 66, 68]

18; 39,777

NA

NA

NA

1.00 (0.99–1.01)

 Climatic zone

  Tropical or Subtropical [61, 65, 67, 69, 70]

5; 2464

1.13 (1.00–1.29)

1.06 (0.97–1.16)

0.97 (0.82–1.15)

0.97 (0.77–1.21)

  Temperate [28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60, 62,63,64, 66, 68]

38; 46,856

0.99 (0.99–1.00)

0.99 (0.98–1.00)

0.99 (0.97–1.00)

0.99 (0.97–1.01)

 Summer

  Summer-inclusive [32, 34, 36,37,38, 40, 42, 43, 46,47,48,49, 51, 52, 54,55,56,57,58,59, 62,63,64,65,66,67,68,69,70]

29; 44,896

1.01 (0.99–1.02)

1.01 (0.98–1.04)

1.01 (0.98–1.03)

1.00 (0.98–1.02)

  Summer-sparing [28,29,30,31, 33, 35, 39, 41, 44, 45, 50, 53, 60, 61]

14; 4424

0.83 (0.75–0.92)

0.77 (0.67–0.88)

0.79 (0.69–0.90)

0.85 (0.74–0.98), 26

 Winter

  Winter-dominant [28,29,30,31, 35, 39, 44, 45, 60]

9; 1961

0.72 (0.62–0.82)

0.70 (0.61–0.81)

0.80 (0.71–0.90)

0.79 (0.71–0.89), 10

  Winter-non-dominant [32,33,34, 36,37,38, 40,41,42,43, 46,47,48,49,50,51,52,53,54,55,56,57,58,59, 61,62,63,64,65,66,67,68,69,70]

34; 47,359

1.00 (0.99–1.02)

1.01 (0.98–1.03)

1.00 (0.98–1.03)

1.00 (0.98–1.02)

Sensitivity analysis

 Type of ARIs

  Mixed upper and lower respiratory tract infections [29, 32,33,34,35, 42, 48, 49, 53,54,55,56, 60, 62,63,64,65,66,67]

19; 21,974

1.00 (0.98–1.03)

1.01 (0.97–1.05)

1.01 (0.97–1.06)

1.00 (0.97–1.03)

  Upper respiratory tract infections [28, 38,39,40,41, 43, 45,46,47, 50, 52, 54, 57,58,59, 61, 68]

17; 22,395

0.99 (0.94–1.00)

0.99 (0.91–1.00)

0.99 (0.92–1.00)

0.98 (0.96–1.01)

  Lower respiratory tract infections [30, 36, 37, 51, 54]

5; 4305

0.98 (0.80–1.12)

0.95 (0.82–1.09)

0.95 (0.79–1.13)

0.95 (0.83–1.08)

  Influenza [31, 44, 52, 53, 55, 58, 59, 61, 69]

9; 3594

0.98 (0.88–1.08)

0.96 (0.80–1.13)

0.96 (0.80–1.15)

0.98 (0.89–1.07)

  1. The dose–response meta-analysis could not achieve convergence on age group: 7–17 years, dosing frequency: weekly, and trial duration: > 12 months. The sample size was too small for dosing frequency: bolus to perform dose–response analysis. NNT was calculated for those meta-analyses showing significant preventive results
  2. ARI Acute respiratory infection, NA Not available, NNT Number needed to treat
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Nutrition Journal

ISSN: 1475-2891

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