| Methods |
CBA. Outcome assessment was not undertaken blind to treatment group allocation. Completeness of follow‐up not applicable because of population‐based design. Assessment of distribution of confounders presented. The areas were well balanced in terms of climate, population, ethnic groupings, education levels, unemployment levels and mean household income. |
| Participants |
3‐year campaign reporting 9827 helmet observations in 5 to 15 year‐olds in Seattle and Portland, US |
| Interventions |
Subsidised helmets, helmet education and a television and media campaign. The control group received none of the above interventions. |
| Outcomes |
Observed helmet wearing. Measured at 4, 12 and 16 months. 4‐month data used in meta‐analysis. |
| Notes |
This large geographical study compared observed helmet wearing before and after a promotion campaign in one area (Seattle) with changes in observed helmet use in a distinct control area (Portland). This analysis uses unadjusted helmet wearing rates (rates adjusted for confounding also reported). |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Allocation concealment (selection bias) |
High risk |
Not used |
