Abstract
BackgroundBicycle helmet laws generally increase helmet usage, but few studies assess whether helmet laws reduce disparities. The objective of this study is to assess changes in racial/ethnic disparities in helmet use among high school students in urban jurisdictions where laws were previously determined to increase overall helmet use.MethodsLog-binomial models were fit to four districts’ 1991–2013 Youth Risk Behavior Survey (YRBS) data. Post-regression predictive margins were used to calculate adjusted bicycle helmet use proportions, assess before-to-after changes in race/ethnicity specific helmet use, and estimate changes in disparities from jurisdictions’ white subpopulations.ResultsHelmet use among white students increased by 10.2 percentage points in two Florida counties (p < 0.001), 20.1 points in Dallas (p < 0.001), and 24.4 points in San Diego (p < 0.001). Increases among African Americans were 6.1 percentage points in the Florida counties (p < 0.001), 8.2 points in Dallas (p < 0.001), and 6.3 points in San Diego (p = 0.070). Use increased among Latino students in the Florida counties (4.3 percentage points, p = 0.016) and Dallas (6.2, p = 0.002), but not significantly in San Diego. San Diego helmet use among Asian students increased by 12.8 percentage points (p < 0.001). Because helmet use increased more for white students, helmet laws were associated with increased disparities. In the Florida counties, disparities increased significantly by 5.9 percentage points for Latino students (p = 0.045). San Diego disparities worsened by 18.1 (p < 0.001), 21.3 (p < 0.001), and 11.6 (p = 0.013) percentage points among African American, Latino, and Asian students respectively. Dallas disparities increased by 11.9 (p = 0.015) and 14.0 (p = 0.003) percentage points among African American and Latino students. Increased disparities generally persisted for follow-up time of at least a decade. Main study limitations include the possibility of helmet use reporting error and limited socioeconomic variables in YRBS datasets.ConclusionsHelmet use increased across racial/ethnic subpopulations, but greater increases among white students increased disparities. Policymakers should couple laws with other approaches to reduce helmet disparities and cycling injuries.Electronic supplementary materialThe online version of this article (doi:10.1186/s40621-016-0086-3) contains supplementary material, which is available to authorized users.
Highlights
Bicycle helmet laws generally increase helmet usage, but few studies assess whether helmet laws reduce disparities
A three-city study of 5th graders in Birmingham, Alabama; Houston, Texas; and Los Angeles County, California, found that white students were over 30 percentage points more likely to wear helmets than their African American or Latino counterparts
This study extends an earlier analysis that found helmet laws increased bicycle helmet use among high school students in four urban public school districts using a variety of strategies for causal inference (Kraemer 2016)
Summary
Bicycle helmet laws generally increase helmet usage, but few studies assess whether helmet laws reduce disparities. Helmet laws inducing a high degree of compliance would be expected to reduce disparities as helmet use across subpopulations converge near universality. Achieving such rates would likely require cyclists to believe enforcement is common and penalties are meaningfully large (Polinsky & Shavell 2007; Jennings & Mieczkowski 2011). If helmet laws serve primarily an informational or norm-setting function, effects may vary across subgroups proportional to the extent to which laws change perceived benefits of helmet use or behavioral norms. Laws may engender smaller effects among more marginalized populations even if there is no difference in expected benefits if costs of compliance are proportionally greater (National Highway Traffic Safety Administration 2004)
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