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Table 1 Summary of the characteristics of the included studies a

From: A meta-analysis of the reproducibility of food frequency questionnaires in nutritional epidemiological studies

  Overall Adult Old Adolescent
Range of age (years) 8–86 18–50 >  50 8–17
Number of studies 124 78 33 15
Population characteristics
Total number 20,830 11,336 7897 1597
Sample size 112 (14–1981) 102 (20–1623) 158 (14–1981) 101 (48–185)
Distribution of gender
 Region
  Africa 6 (4.88) 5 (6.49) 0 (0) 1 (6.67)
  Oceania 8 (6.50) 5 (6.49) 2 (6.07) 1 (6.67)
  Asia 37 (30.08) 22 (28.57) 11 (33.33) 4 (26.67)
  Europe 35 (28.46) 22 (28.57) 10 (30.30) 4 (26.67)
  America 37 (30.08) 23 (29.87) 10 (30.30) 5 (33.33)
FFQ design characteristics
 Items of FFQ
  ≥ 120 61 (49.59) 41 (53.25) 15 (45.45) 5 (33.33)
  < 120 62 (50.41) 36 (46.75) 18 (54.55) 10 (66.67)
 Dietary recall intervals
  ≥ Previous 12 months 80 (65.04) 50 (64.94) 28 (84.85) 4 (26.67)
  < Previous 12 months 33 (26.83) 20 (25.97) 3 (9.09) 10 (66.67)
  Not available 10 (8.13) 7 (9.09) 2 (6.06) 1 (6.667)
Characteristics of the reproducibility studies
 Administration mode of FFQ
  Interview-administered 44 (35.77) 29 (37.66) 12 (36.36) 4 (26.67)
  Self-administered 63 (51.22) 36 (46.75) 19 (57.58) 9 (60.00)
  Not available 16 (13.01) 12 (15.59) 2 (6.06) 2 (13.33)
 Intervals between FFQs
  < 6 months 63 (51.22) 45 (58.44) 8 (24.24) 12 (80.00)
  ≥ 6 months 55 (44.72) 29 (37.66) 23 (69.70) 3 (20,00)
  Both intervals 5 (4.06) 3 (3.90) 2 (6.06) 0 (0)
  1. aValues are N (%) or median (range)