Dear Editor

Such as the paper from Dales et al. concerning the influence of family income on asthma morbidity,[1] understanding socioeconomic effects on adolescent health is a critical and important area of research if we are to eliminate health disparities.[2] Moreover, traditionally used tools to evaluate socio-economic gradient are difficult to construct within this population and new indicators must be developed for more specific measurements of the socio-economic status of adolescents.[3] Thus, a cross-sectional analysis of the 1998 cross- national study "Health Behaviour of School aged Children " (HBSC) in French-speaking Belgium was undertaken.

The survey was based on a self- completed questionnaire concerning various aspects of physical and social health. The health problems (asthma and any other respiratory difficulty) were considered present when a positive reply was given to close-end questions stating if the pupils suffered, or have suffered from these problems during the last six months. We analysed a representative sample of 12,012 pupils aged 11 to 19 years in fifth and sixth grades of primary school, and in all six grades of secondary school. Socio-economic variables where "the perceived family economic status" and a family economic score. This score combines three variables: "has a room for him/herself", "family has a car or a van" and "number of holidays with parents over the last year". This score is more adapted like measures of economic status [4] rather than traditional indicators (occupation of the father, current work of the parents, family incomes). The overall prevalence of self-reported asthma is 6.6 % and asthma shows significant differences according to sex (more for girls ), age (more when 17-19 years old), nationality (more in Belgians than among foreigners). No difference is found for socio-economic score. However, 21.1 % of the pupils say having had respiratory difficulties during the last 6 months and the prevalence of this affection increases with age, is more significantly reported by girls than boys and by pupils from vocational and technical types of education, by those having no sibling and/or being in a single- parent or recomposed family and by pupils reporting poorer economic conditions.

In our study, active smoking is not a risk for self reported asthma in adolescence but is nonetheless significantly associated with self-reported respiratory difficulties. Our results confirm socio-economic predictors of respiratory health problems in adolescence. Subjective respiratory health problems present a significant socio-economic gradient. Pupils with a lower economic score have a higher prevalence of subjective complaints concerning their health compared with the more favoured groups. More studies must make it possible to understand the mechanisms that may underline symptom reports and self- assessment of general health status.

References

(1) Dales RE, , Choi B, Chen Y and Tang M. Influence of family income on hospital visits for asthma among Canadian school children. Thorax 2002;57:513-7.

(2) Goodman E. The role of socioeconomics status gradients in explaining differences in US adolescents'health. Am J Public Health 1999;89:1522- 28.

(3) Coppieters Y, Piette D, Kohn L, De Smet P. Health inequalities: self- reported complaints and their predictors in pupils from Belgium. Revue d'Epidémiologie et de Sante Publique 2002 ;50(2):135-46.

(4) Currie CE, Elton RA, Todd J, Platt S. Indicators of socioeconomics status for adolescents : the WHO Health Behaviour in School-aged Children Survey. Health Educ Research 1997;12:385-97.