Association of average daily corticosteroid dose with time to relapse in children with idiopathic nephrotic syndrome: Results from a longitudinal cohort study

Background In this longitudinal cohort study, we aimed to determine the association between average daily corticosteroid dose and time to first relapse among children with first presentation of nephrotic syndrome. Method We enrolled children (1–18 years) with nephrotic syndrome at the time of first presentation of nephrotic syndrome across 11 Canadian centers in the CHILDNEPH study between 2013–2019. Exposure was within-person average daily corticosteroid dose. Primary outcome was time to first relapse after entry into the study. Cox proportional hazards regression models were created to estimate the risk of relapse after adjusting for potential confounders. Results Among 328 children (129 females) with median age 4.3 (IQR 3.6) years, the unadjusted median time to first relapse in the study was 128 (42–707) days. The relationship between average daily corticosteroid dose and time to relapse was modified by age (HR: 0.87, 95% CI 0.82–0.93) with younger children having a higher risk of relapse compared to older children for the same corticosteroid dose. Relationships between time to first relapse, average corticosteroid dose, and age remained unchanged when including those children who entered the study at first or second relapse or those who relapsed while tapering the prednisone during the episode at entry in the study. Conclusion Younger children, despite receiving same average daily corticosteroid dose, experience faster time to relapse compared to older children. Further study is warranted to examine the optimal dosing of corticosteroids by age of the child.