Comorbidity of Type 1 Diabetes and ADHD: A Longitudinal Cohort Study in Males and Females From the Norwegian Childhood Diabetes Registry

Aims This study of interactions between attention‐deficit hyperactivity disorder (ADHD) and type 1 diabetes has two aims. First, compare the prevalence of prescribed ADHD medications in individuals with type 1 diabetes to the general paediatric population in Norway. Second, study trajectories in mean glycated haemoglobin (HbA1c) in individuals with comorbid ADHD in comparison to individuals with type 1 diabetes only. Methods Part 1 uses data from the Norwegian Prescription Database and register linkage between the Norwegian Childhood Diabetes Registry (NCDR) and the Norwegian Prescribed Drug Registry to obtain yearly prevalence in the general population and NCDR between 2005 and 2019. Part 2 uses data from annual controls in NCDR between 2005 and 2022. Linear mixed‐effects models adjusted for age and diabetes duration were used to compare mean HbA1c in 365 individuals (66% males) with comorbid ADHD to 5,888 individuals (54% males) with type 1 diabetes only. Results Part 1: Yearly prevalence (2009–2019) ranged from 0.02 to 0.52 percentage points higher in NCDR than in the general population. The difference was significant only for 2017. Part 2: Mean national HbA1c decreased from 2012 to 2022 but was higher in individuals with comorbid ADHD. This difference was significant from 2016 (67.6 mmol/mol [8.3%] vs. 64.5 mmol/mol [8.1%]) to 2022 (57.5 mmol/mol [7.4%] vs. 54.7 mmol/mol [7.2%]). When grouped by sex, these differences continued to be significant in males (except in 2018), but not in females. Individuals with ADHD were more likely to have experienced at least one episode of diabetic ketoacidosis (odds ratio [OR] = 1.39, 95% confidence interval [CI] [1.04, 1.86]; males: OR = 1.65, 95% CI [1.15, 2.36]; females: OR = 1.10, 95% CI [0.658, 1.83]). Conclusion Mean national HbA1c decreased in Norway during the last decade, but continued to be higher in individuals with comorbid ADHD than in individuals with type 1 diabetes only.