Age-related slowing on the Digit Symbol task: longitudinal and cross-sectional analyses.

It is generally known that slowing on tasks like the Digit Symbol Substitution task occurs with age. However, simultaneous cross-sectional and longitudinal data are rare. The results from the cross-sectional analysis of Digit Symbol performance with age are compared to results from two occasion longitudinal analyses on the same task. The longitudinal data were obtained from 79 participants who were retested after 7 years and were between the ages of 48 and 73 years old at Time 1. Results indicated that the pattern of actual change observed in the longitudinal analyses replicated the simulated change indicated in the cross-sectional analysis. Antecedents were examined using the original cross-sectional sample of 150 participants. Significant relationships with Digit Symbol performance were found for age, education, and gender, but not for ratings of physical health.