Table 1 Characteristics of included studies.
| Study | Type | Blinding | Completeness of follow‐up | Balanced confounders | Age range (years) | Numbers of participants* | Setting | Intervention | Measurement of outcome | Baseline observations | In meta‐analysis |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Britt, 199817 | CBA | N | N | NR | 3–4 | I = 680 children (14 sites) | Community+School | F+E | T (1) = 2W | I = 99/230 (43.0%) | Y |
| C = 200 children (4 sites) | C = 30/71 (42.3%) | ||||||||||
| Cote, 199218 | CBA | N | NA | Median income I >C | <16 | Total observations = 328 | Community | S+E | T (1) = 9M | I = 11/140 (7.9%) | Y |
| C = 7/37 (18.9%) | |||||||||||
| DiGuiseppi, 198919 | CBA | N | NA | Y | 5–15 | Total observations = 9827 | Community | S+E | T (1) = 4M | I = 50/905 (5.5%) | Y |
| T (2) = 12M | C = 11/1052 (1.0%) | ||||||||||
| T (3) = 16M | |||||||||||
| Farley, 199620 | CBA | N | NA | NR | 5–12 | I = 50 000 children (244 schools) | Community | F+S+E | T (1) = 12M | NR | Y |
| C = 6513 children | T (2) = 24M | ||||||||||
| T (3) = 36M | |||||||||||
| Floerchinger, 200021 | CBA | N | NA | NR | 5–12 | I = 4 schools | School | E | T (1) = 5M | I = 24/59 (40.7%) | Y |
| C = 19 schools | C = 97/284 (34.2%) | ||||||||||
| Hall, 200416 | cRCT | N | Y | Y | 5–12 | I = 13 schools | School | E | T (1) = 6M | I = 455/512 (88.9%) | Y |
| C = 14 schools | T (2) = 18M | C = 559/603 (92.7%) | |||||||||
| Liller, 199522 | CBA | N | NA | NR | 5–8 | I = 3428 children (9 schools) | School | S+E | T (1) = 2W | I+C = 46/543 (8.5%) | Y |
| C = 9 schools | |||||||||||
| Moore, 199023 | CBA | N | NA | NR | 11–13 | I = 1 school | School | S+E | T (1) = 6W | NR | N |
| C = 1 school | T (2) = 10W | ||||||||||
| Morris, 199113 | cRCT | N | NR | NR | 5–13 | I (1) = 1 school | School | I(1) S+E | T (1) = 1M | I (1) = 0/22 (0%) | Y |
| I (2) = 1 school | I(2) E | I (2) = 0/25 (0%) | |||||||||
| C = 1 school | C = 0/22 (0%) | ||||||||||
| Parkin, 199324 | CBA | N | NA | Y | 5–14 | I = 1100 children (4 schools) | School | S+E | T (1) = 2M | I = 13/420 (3.1%) | Y |
| C = 18 schools | C = 15/482 (3.1%) | ||||||||||
| Parkin, 199514 | CBA | N | NA | Y | 5–14 | I = 1415 | School | I(1) S+E | T (1) = 2M | I (1) = 5/129 (3.9%) | Y |
| I(2) E | I (2) = 1/152 (0.7%) | ||||||||||
| C = 7/246 (2.8%) | |||||||||||
| Towner, 199215 | cRCT | N | NA | NR | 5–12 | I = 3 schools | School | S+E | T (1) = 2W | I = 3/556 (0.5%) | Y |
| C = 3 schools | T (2) = 4M | C = 11/369 (3.0%) | |||||||||
| Total children = 2211 | |||||||||||
| Wright, 199525 | CBA | N | NA | C older than I | 11–18 | Total observations = 741 | School | E | T (1) = 2W | NR | N |
C, control; CBA, controlled before/after study; cRCT, cluster randomized controlled trial; E, education/promotion program; F, free helmets; I (n), intervention (arm n); M, months; N, no; NA, not applicable; NR, not reported; RCT, randomized controlled trial; S, subsidized helmets; T (n), time point (n); W, weeks; Y, yes.
*Where number of children or schools is not included in the table this is due to data not reported in publications.