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Byline: C. W. Schnohr (1), S. Kreiner (2), E. P. Due (1), C. Currie (3), W. Boyce (4), F. Diderichsen (1) Keywords: Family affluence scale; Differential item functioning; Health Behaviour in School-aged Children (HBSC); Comparability; Validity Abstract: Methodology for making cross-national comparisons is an area of increasing interest in social and public health related research. When studying socio-economic differences in health outcomes cross-nationally, there are several methodological issues of concern, especially when data is derived from self-reported questionnaires. Health Behaviour in School-aged Children (Currie et al. 1998) is a WHO cross-national study using school samples. HBSC provides comparable data, and thereby a unique opportunity to study associations between social indicators and health outcomes within an international perspective. In 2001/02 data was collected from a total of 162,323 children in 32 countries (Austria, Belgium, Canada, Croatia, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Greenland, Hungary, Ireland, Israel, Italy, Latvia, Lithuania, Macedonia, Malta, Netherlands, Norway, Poland, Portugal, Russia, Slovenia, Spain, Sweden, Switzerland, Ukraine, United Kingdom, USA.). Studies of social inequalities requires that a comparable measure of socio-economic position (SEP) is in use. HBSC has developed a proxy for social position measuring material wealth, the Family Affluence Scale (FAS). This paper studies FAS and whether it is comparable across population subgroups defined by country, age and gender. Initial analysis revealed that an item measuring perceived family wealth was a valid FAS item. Including this item in the FAS score will improve the reliability of FAS. Graphical log-linear Rasch models (GLLRM) showed that FAS contain differential item functioning (DIF) with respect to country, age, and gender as well as local dependency (LD) between items. During the analysis, test equating techniques where used to adjust for the test bias generated by DIF. We recommend that the equated scores are used whenever FAS is included as a variable. This study suggests that HBSC-FAS should contain five items (additional item: perceived family wealth) when analysing data from HBSC 2001/02, and furthermore that each country should adjust for the DIF or make use of the converted FAS scores provided. If using FAS as a proxy for social position at an international level, it is not advised to compare the absolute levels of FAS, but weigh the scale by ridit transformation. Author Affiliation: (1) Department of Social Medicine, Institute of Public Health, University of Copenhagen, Oester Farimagsgade 5, P.O. Box 2099, Copenhagen, 1014, Denmark (2) Department of Biostatistics, Institute of Public Health, University of Copenhagen, Copenhagen, Denmark (3) Child and Adolescent Health Research Unit, University of Edinburgh, Edinburgh, Scotland (4) McArthur Hall, Queen's University, Kingston, Ontario, Canada Article History: Registration Date: 12/11/2007 Received Date: 25/04/2007 Accepted Date: 10/11/2007 Online Date: 24/11/2007

The objective of the study was to investigate whether there is equalisation of socioeconomic differences in injury risks among Swedish children and adolescents. Equalisation was defined as a reduction in relative differences in risks between socioeconomic groups. All Swedish children and adolescents aged 5-19 in 1990 were grouped into three age cohorts and allocated to four household socioeconomic statuses, considering boys and girls separately. Each cohort was then followed up over a 5-year period (1990-1994) with regard to three injury diagnosis groups (as registered in the national Hospital Discharge and Causes of Death registers) with documented socioeconomic differences: injuries due to traffic, interpersonal violence, and self-infliction. The Relative Index of Inequality was used to measure the magnitude of relative socioeconomic differences, for each year of observation. Where applicable, relative risks were computed in order to see whether equalisation benefited all socioeconomic groups. Tendencies of equalisation were found among girls for two of the diagnosis groups: in traffic injuries for the youngest cohort (aged 5-9 in 1990) and in the case of self-inflicted injuries within the two older cohorts (10-14 and 15-19, in 1990). In conclusion, this study provides limited evidence of equalisation in injury risks between socioeconomic groups among Swedish adolescents. Equalisation appears to be a gender-specific phenomenon, that is, among girls, and manifests itself around the age of 5-13 in traffic-related injuries, when girls are in first and second levels of compulsory school, and later on in self-inflicted injuries. Given the economic recession in Sweden at the time of the study period, whether the equalisation processes are attributable to school, peer group and youth culture effects--as hypothesised by West--is debatable, particularly in the case of self-inflicted injuries. Keywords: Equalisation process: Socioeconomic inequality: Intentional and unintentional injuries: Childhood: Youth: Sweden