Children's Relative Age and Medicine Treatment for Attention-Deficit/Hyperactivity Disorder Across Australian Jurisdictions with Different School Enrolment Policies

Claudia Bruno; Alys Havard; Mark Hanly; Kathleen Falster; Natasha Nassar; Ben Edwards; Adam J Guastella; Sallie-Anne Pearson; Helga Zoega

doi:10.1089/cap.2022.0032

Children's Relative Age and Medicine Treatment for Attention-Deficit/Hyperactivity Disorder Across Australian Jurisdictions with Different School Enrolment Policies

J Child Adolesc Psychopharmacol. 2022 Aug;32(6):349-357. doi: 10.1089/cap.2022.0032. Epub 2022 Jul 15.

Authors

Claudia Bruno¹, Alys Havard^{1

2}, Mark Hanly¹, Kathleen Falster³, Natasha Nassar^{4

5}, Ben Edwards⁶, Adam J Guastella⁷, Sallie-Anne Pearson^{1

5}, Helga Zoega^{1

8}

Affiliations

¹ Centre for Big Data Research in Health, Faculty of Medicine and Health, University of New South Wales, Sydney, Australia.
² National Drug and Alcohol Research Centre, and Faculty of Medicine and Health, University of New South Wales, Sydney, Australia.
³ School of Population Health, Faculty of Medicine and Health, University of New South Wales, Sydney, Australia.
⁴ Children's Hospital at Westmead Clinical School and Faculty of Medicine and Health, University of Sydney, Sydney, Australia.
⁵ Menzies Centre for Health Policy and Economics, Faculty of Medicine and Health, University of Sydney, Sydney, Australia.
⁶ Centre for Social Research and Methods, College of Arts and Social Sciences, Australian National University, Canberra, Australia.
⁷ Brain and Mind Centre, Children's Hospital Westmead Clinical School, Faculty of Medicine and Health, University of Sydney, Sydney, Australia.
⁸ Centre of Public Health Sciences, Faculty of Medicine, University of Iceland, Reykjavík, Iceland.

PMID: 35917527
DOI: 10.1089/cap.2022.0032

Abstract

Background: Children who are relatively young for their school grade are more likely to receive treatment for attention-deficit/hyperactivity disorder (ADHD). It is unclear whether the phenomenon also exists across Australia or is impacted by the school enrolment policy in place. Objective: We evaluated the association between children's relative age and initiation of ADHD medicines across Australian jurisdictions with different school enrolment policies and rates of delayed school entry. Methods: We used Australia-wide dispensing data for a 15% random sample of children 4-9 years of age in 2013-2017 to create a nationwide cohort. Due to high rates of delayed school entry in New South Wales (NSW), we used linked prescribing and education data for a cohort of NSW residents starting school in 2009 and 2012. We estimated incidence rate ratios (IRRs) for ADHD medicine across children's birth month, sex, and jurisdiction. We used asthma medicines as a negative control. Results: For girls, we observed a relative age effect in three out of five jurisdictions, with an IRR ranging from 1.3 to 2.8, comparing the youngest versus oldest birth month thirds. We observed more modest effects among boys, ranging from null to 1.5-fold. In NSW, the relatively youngest boys were less likely to initiate stimulant medicines than the oldest (IRR = 0.5, 95% confidence interval 0.29-0.78). We did not observe a relative age effect for initiation of asthma medicines. Conclusions: In jurisdictions with low rates of delayed entry, relatively young children were more likely to initiate ADHD medicines than their older classmates. We observed the inverse association in NSW where delayed entry was highest, likely reflecting the characteristics and needs of children who delay school entry for 1 year and become the oldest children in the grade. Increased awareness around children's maturity differences and school readiness may enhance appropriate diagnosis and treatment of ADHD.

Keywords: CNS stimulants; attention-deficit/hyperactivity disorder; child health; relative age.

MeSH terms

Age Factors
Asthma*
Attention Deficit Disorder with Hyperactivity* / diagnosis
Attention Deficit Disorder with Hyperactivity* / drug therapy
Attention Deficit Disorder with Hyperactivity* / epidemiology
Australia
Child
Child, Preschool
Female
Humans
Male
Policy
Schools