The social patterning of road traffic injuries during childhood and youth : national longitudinal register-based studies

Sammanfattning: Apart from being the primary cause of death during childhood and adolescence, scientific evidence points in the direction that road traffic injuries make a major contribution to social inequalities in health during this period of life. The aim of the thesis is to advance knowledge and understanding of social differences in road traffic injury morbidity among young people in Sweden. The thesis is composed of five register-based nation wide cohort studies. In the first study, socioeconomic group of the household is studied in relation to hospital-based road traffic injuries as pedestrians, bicyclists, moped-riders, motorcyclists and car drivers, for the period 19871994 (when subjects were aged 2-24 years). Morbidity differences between groups are observed in all categories of road users, but most prominently among motorized-vehicle drivers. In spite of more injuries occurring among boys than girls, similar social patterning emerges for both sexes. The following two studies investigate whether the social distribution of road traffic injuries for different age groups and for different types of road users varies according to how socioeconomic position of the family is measured. Consideration is paid to parental education, socioeconomic group of the household (based on occupation) and household disposable income. Among young children (Study II), road traffic injuries as pedestrians, bicyclists, and car passengers are studied for the years 1991-1999, and among older ones (Study III), road traffic injuries as car drivers for the years 1991-1996. The groups were followed respectively up to 14 years and up to 23 years. It is observed that both parental socioeconomic group and parental education impact on the risk of road traffic injuries in the two age groups. By contrast, disposable income of the household is a risk factor of greater importance among the younger ones. Studies IV and V focus on young adult car drivers and distinguish their socioeconomic position of origin, based on the socioeconomic group of the household, and their position of destination, considering subject's educational attainment at age 28-30 years. In study IV, the social patterning of injury repeaters is examined as compared to that of the once-injured, based on in-patient treatment when subjects were aged 18-26 years, an age period otherwise at high risk of injuries as car drivers. The study shows that injury repeaters as car drivers are uncommon and that their social patterning is much similar to that of once-injured drivers. For Study V, car-to-car and single crashes are analysed, paying attention to various injury severity levels (consequences) and various crash patterns (circumstances). Crash data come from the police reports for the period 1988-2000, i.e., when subjects were 18-30 years. Relative risks of road traffic injuries are compiled considering age at licensing of the subjects. Socioeconomic differences appear clearly for both crash consequences and crash circumstances. The excess risk for young drivers from lower socioeconomic groups is more pronounced as severity increases. Whereas gender modifies the effect of socioeconomic position of destination, it does not modify the effect of socioeconomic position of origin. The results of the studies forming the thesis suggest differences in the impact of road traffic injuries among children and young people from different socioeconomic group in Swedish society. Further, the excess risk for young drivers from lower socioeconomic groups is consistent across crash severity levels, and becomes more pronounced as severity increases.