Norwegian normative data for regression-based D-KEFS color-word interference test derived measures and comparison to conventional contrast measures

The Delis Kaplan Executive Functions system (D-KEFS) Color-Word Interference Test (CWIT) is a neuropsychological test of executive function. The CWIT, an expanded version of the Stroop test, includes contrast measures created by subtracting lower-level conditions from higher-level conditions. These measures do not have available Norwegian norms and have been criticized for their low reliability. For this reason, we present normative data for regression-based derived measures based on a large sample of healthy Norwegians aged 20-85 years and compare the regression measures to conventional contrast measures. The study sample comprised 1011 healthy participants between ages 20 and 85, pooled from three cohorts: the Dementia Disease Initiation cohort (DDI), the Oslo MCI cohort, and the Lifespan Changes in Brain and Cognition cohort (LCBC). Multiple regression analyses were used to model the effects of the lower-level reading or naming conditions on higher-level inhibition or inhibition/switching conditions. Conventional contrasts and regression-based derived measures were assessed for residual effects of demographics and lower-level CWIT conditions. Stability over time was examined in a sub-sample with available follow-up data. Conventional contrasts showed residual effects of demographics and basic functions. Analyses of stability over time showed ICCs in the poor to moderate range (range = 0.39-0.56) for conventional contrasts and somewhat higher estimates for the regression measures (range = 0.50-0.65). As such, the regression-based derived measures adequately adjust for demographics and lower-level conditions and show better stability over time compared to conventional D-KEFS contrast measures. To fully understand the clinical applicability of regression-based derived measures, future work should include clinical samples.