Socio-economic inequities in children's injury rates: has the gradient changed over time?

INTRODUCTION: Changing socio-economic gradients in adult health over time have been documented, but little research has investigated temporal changes in child health gradients. Childhood hospitalizations for injury have fallen over the last two decades; whether the socio-economic gradient in childhood injury has changed is unknown.
METHODS: Population-based hospital discharge data were used to calculate rates of hospitalization for injury from 1986/87 through 2005/06 for all children under 20 years of age in Manitoba (average yearly number of hospitalizations = 326,357). Information on socio-economic status (SES) came from area-level census data and was assigned by residential postal codes. Generalized linear models with generalized estimating equations were employed to describe the relation between SES and injury rates and whether this relation changed over time. All-cause injuries were examined as well as injuries for motor vehicle collisions (MVCs), other vehicle injuries, self-inflicted injuries, assault, poisoning, injuries caused by machinery, sports injuries and falls.
RESULTS: Injury hospitalizations for children decreased steadily over the study period, from 1.07% to 0.51%. SES significantly predicted injury hospitalizations (p < 0.0001), children with lower SES showing higher rates. A significant SES by year interaction (p < 0.0001) indicated that the SES gradient for injury hospitalizations increased over time. Analysis by type of injury found a significant SES by year interaction for MVCs, self-inflicted injuries and falls; for MVCs and self-inflicted injuries the pattern (increasing SES gradient) was similar to that of hospitalization for all-cause injury. The pattern for falls was inconsistent.
CONCLUSION: Despite the overall drop in injury hospitalizations over time, the SES gradient in hospitalized injury rates has increased.