Abstract
There is some evidence that children with asthma perform less well academically compared to healthy children. However, the role of parental socioeconomic status, own comorbidities, e.g. attention deficit hyperactivity disorder (ADHD) and other family factors is not clear. Using sibling comparisons makes it possible to take family factors into account, as it enables us to adjust for everything siblings have in common.
We performed a study based on all children born in Sweden by Swedish born parents and who graduated from the 9th grade of school in 2008-2013 (n= 481 291). By linkage between Swedish national registers we retrieved information on school grades from 9th grade (transformed to percentiles by year of graduation), specialist diagnoses of asthma and asthma medication dispenses, information on the potential confounders sex, ADHD, birth weight, gestational age, parental asthma and education, and information on sibship within the cohort (87 459 families with 2-5 siblings). Asthma was defined as either ≥2 dispenses of asthma medication and/or ≥1 specialist diagnosis in grade 7-8. Data was analysed by linear regression in the full study population and fixed effect linear regression for comparisons within sibships discordant for asthma.
Children with asthma had slightly better grades than children without asthma when adjusting for measured potential confounders (β=1.3; confidence interval (CI) 1.1-1.6). When also adjusting for familial factors using sibling comparison the difference was halved (β=0.6; CI 0.0-1.1).
In conclusion children with asthma had slightly better grades than children without asthma, although partly confounded by factors shared within the family.
- Copyright ©the authors 2016