Longitudinal medication adherence in children with nephrotic syndrome and association with disease outcomes

ABSTRACT Background Children with nephrotic syndrome have a high medication burden and treatment-related side effects, which can contribute to non-adherence. Optimal medication adherence may reduce symptom burden, improve disease control and prevent complications. However, longitudinal patterns of medication adherence and associations with disease outcomes among children with nephrotic syndrome remain uncertain. Methods We analysed data from Insight into Nephrotic Syndrome: Investigating Genes, Health, and Therapeutics, a prospective observational childhood nephrotic syndrome cohort. We included all children (1–18 years of age) with nephrotic syndrome diagnosed from 1996 to 2023 from the Greater Toronto and Hamilton Area, Canada, excluding congenital or secondary causes of nephrotic syndrome. Participants were followed annually with questionnaires for up to 5 years since study initiation. Medication adherence was self-reported by participants or parents using the Medication Adherence Questionnaire (MAQ). We evaluated the association between longitudinal medication non-adherence (MAQ score ≥1) and subsequent relapse rates, steroid-sparing medication initiation and hospitalizations using generalized linear mixed models. Results We included 1905 study visits among 735 children diagnosed with nephrotic syndrome [mean age at visit 8.7 years (standard deviation 4.3), 65% male, 30% frequently relapsing or steroid dependent, median 1 (interquartile range 0–3) prescribed medications]. Medication non-adherence (MAQ score ≥1) was reported at 367 (19%) study visits and 228 (31%) participants reported non-adherence at least once. Rates of non-adherence remained stable over 5 years of follow-up. Worse medication adherence was not significantly associated with subsequent relapse rates {adjusted relative rate 1.14 [95% confidence interval (CI) 0.97–1.34]}, use of steroid-sparing medication [adjusted odds ratio (OR) 0.90 (95% CI 0.61–1.32] or rituximab [adjusted OR 0.77 (95% CI 0.36–1.66)] or hospitalizations [adjusted OR 1.17 (95% CI 0.59–2.32)]. Conclusions Self-reported medication non-adherence occurs in one-third of children with nephrotic syndrome yet does not adversely affect subsequent relapses, steroid-sparing medication use or hospitalizations.