Age-related variables in childhood epilepsy: how do they relate to each other and to quality of life?

How do age of onset and duration of epilepsy correlate with each other and with patient-reported outcomes? To address this question, we explored whether age of onset, duration, and proportion of life with epilepsy are either similar or relatively independent variables that can be used as markers on how children experience the complexity of epilepsy and adjustment. Three hundred ninety-one Canadian and 266 Hong Kong youth with epilepsy completed the childhood epilepsy-specific quality of life (QOL) measure (CHEQOL-25). Each cohort was separately stratified by tertiles for age of onset, life proportion with epilepsy, and duration of epilepsy. Pearson's r was used for correlation analysis. The epilepsy age-related variables correlated strongly with each other among children with epilepsy onset ≤4 years (r = 0.53-0.66). The correlation between these variables was weaker with an onset ≥9 years (r =0.22-0.35). Correlation with QOL was clinically non-significant. These variables appear to measure the same phenomenon only in children with early epilepsy onset (<4 years) and explain little variance in QOL.