Ethnic differences in asthma treatment among Swedish adolescents: A multilevel analysis of individual heterogeneity

Adolescents with immigrant or ethnic minority background suffering from asthma receive on average less appropriate anti-asthmatic medication (AAM) than the majority population. However, those findings are based on analyses of differences between group averages which prevents our understanding of individual heterogeneity around the averages. Taking into account individual socioeconomic factors and medical needs, we performed multilevel analysis in order to evaluate if maternal country of birth (MCOB) accurately identifies adolescents with inappropriate AAM use.

Using the Swedish Medical Birth Register, we identified all singleton children born between 1988 and 1991 who were residing in the country until they turned 17 and had complete information on the study variables. We applied a two-level multilevel logistic regression analysis with 62 MCOBs at the second and 755,894 children at the first level. Adjusting for socioeconomic and medical factors using a risk score, and including the socioeconomic characteristics of the MCOBs, we obtained both measures of association (odds ratio (OR)) and measures of variance (Intra-class correlation (ICC)).

Comparing with adolescents born from Swedish mothers, all other children had a lower AAM use, especially those whose mothers were from upper-middle- and low-income countries (OR = 0.47, 95% confidence interval: 0.35-0.61). However, the ICC was low (i.e., ICC ≈ 3%) for both preventive and relief AAM.

MCOB was associated to adolescent use of AAM. However, the small ICC indicates that MCOB is an inaccurate categorization for identifying inappropriate use of AAM among Swedish adolescents.