Background and aim: In most northern European countries adolescent smoking is most prevalent in lower social classes but there is little information about time trends in social inequality. This paper describes trends in social inequality in daily smoking among adolescents from 1991 to 2006 by both absolute social inequality (prevalence difference between low and high social class) and relative social inequality (prevalence ratio).
Methods: We analysed 15-year-olds from the Health Behaviour in School-aged Children (HBSC) study in Denmark in 1991, 1994, 1998, 2002 and 2006, total n = 6703. The surveys were comparable because of similar procedures for sampling, data collection, and measurements of smoking and parents' occupational social class.
Findings: From 1991 to 2006 the prevalence of daily smoking decreased from 15.9% to 10.9% among boys and from 20.1% to 10.6% among girls. The social inequality fluctuated over time and was different for boys and for girls. The prevalence difference between boys from low and high social class was 5.2% in 1991 and 9.3% in 2006, corresponding figures for girls were 4.8% and 7.0%. The prevalence ratio among boys was 1.38 (in 1991) and 2.19 (in 2006), among girls 1.28 and 1.95.
Conclusions: Daily smoking was most prevalent among students from lower social classes and the level of inequality fluctuated over time. Conclusions on social inequality in adolescent smoking may appear differently when described by absolute and relative measures. The absolute and relative social inequality in adolescent smoking was higher in 2006 than in 1991.