New regression-based norms for the Trail Making Test on Norwegian older adults: Understanding the effect of education

Objective: To produce regression-based norms for older adults on the revised Trail Making Test with alphabet support (TMT-NR3). By examining the potential modulating effects and putative interaction effects of age, education, and sex, we aim to gain insights into cognitive aging and the effects of education. Method: Altogether, 440 healthy participants with an age-span from 70 to 92 years from the NorFAST (n = 249) and the HUNT (n = 191) studies were included. Regression-based norms for TMT-A, TMT-B, and derived measures TMT B-A, TMT B/A, and TMT-β were produced. Models were assessed for pertinent linear, curvilinear, or interaction effects of age, education, and sex. We evaluated and compared our norms to published North American TMT norms. Results: Higher age was linearly associated with lower performance on all measures. No sex differences were found. We found a reduced positive association with education on test performance at higher age. However, this interaction effect was found to be driven by participants with low education. Our validated proposed norms showed a better fit to observed data than the existing norms. Conclusion: The norms were adjusted for age on all measures. Norms without age adjustment are made available for TMT B/A due to a slightly better fit of this model. The results indicate (i) that only processing speed and not set-shifting declines with age and (ii) that the selection process for education might be more important than actual education for older-age performance.