Differences in Outcomes of Mandatory Motorcycle Helmet Legislation by Country-Income Level: A Systematic Review and Meta-Analysis

Background: Even though over 90% of fatal road traffic injuries occur in Low-and-Middle-Income Countries (LMICs) primarily affecting motorcyclists, the utility of helmet laws outside of high-income settings has been undermined. We sought to evaluate the effects of mandatory motorcycle helmet legislation and determine whether the effectiveness differed across country-income levels. Methods: A systematic review and meta-analysis were completed using the PRISMA criteria to evaluate studies on helmet usage, mortality from motorcycle accident, or traumatic brain injury (TBI) incidence, before and after enactment of a mandatory helmet law. Pooled odds ratios and their 95% confidence intervals (CI) were stratified by high-income countries (HICs) vs. LMICs using the random-effects model. Findings: Twenty-four studies were included in the final analysis. All studies demonstrated higher odds of helmet usage; however, the effect was statistically significantly greater in HICs (OR: 73.2; 95% CI: 46.9; 114.3) than in LMICs (OR: 5.05; 95% CI: 2.93; 8.70), p-interaction comparing both strata < 0×01. There was a significantly lower rate of motorcycle fatalities after enactment of helmet legislation (OR: 0×67; 95% CI: 0×56; 0×81with no significant difference by income classification, p-interaction: 0×36. TBI incidence was statistically significantly lower in HICs (OR: 0×53, 95% CI 0×46-0×61) than in LMICs (0×77, 95% CI 0×59-1×01) (p-interaction: 0.01). Interpretation: The recent Lancet Commission on Legal Determinants of Global Health argues that effective law can provide the framework for achieving sustainable development goals. Our findings support that the potential public health impact that could follow implementation of mandatory helmet laws typifies this sentiment and should be a priority of international policy. Funding Statement: None. Declaration of Interests: None.