Age-related changes in executive function and the influence of processing speed

Healthy aging has been associated with declines in executive functioning (EF) but it remains unclear how different subprocesses of EF are affected by age and by other possibly mediating variables. The principal aim of the present study was to investigate the effects of age and processing speed on three executive functions: set-shifting, planning, and attentional control. Four age groups (20-29 years, 60-69 years, 70-79 years, and 80-89 years) were compared on the Wisconsin Card Sorting Test (WCST), the DKEFS Tower Test, the Conner's Continuous Performance Test, and a Letter comparison test of processing speed. Results suggested that increased age was associated with decreased performance on most of the studied executive measures, but not all EF are equally affected by age. A slowdown in processing speed mediates some, but not all, decrements in executive performance. The results are interpreted in light of recent neuroimaging data on age-related changes in brain functioning.