Abstract :
[en] Background and aim. Cognitive aging models propose that cognitive resources available decrease with age, and that older people experience a more pronounced decline in performance over time. Mental fatigue is also known to negatively impact cognitive performance. How available cognitive resources interact with fatigue level across the lifespan remains largely unexplored. Our objective is to identify and compare the effects of an induced mental fatigue state on cognitive performance in young, middle-aged, and older participants.
Methods. 43 young, 25 middle-aged and 19 older people performed a 32-min mental fatigue induction task in condition of high or low cognitive load (HCL/LCL). Cognitive load was modulated by the stimuli time duration (STD), with shorter STD leading to higher cognitive load, and thus, higher mental fatigue across task. A repeated measure ANOVA (p<0.05) was conducted to determine the effects of group (young, middle-aged, older), condition (HCL vs. LCL) and time on task (4 blocks of 8 min) on accuracy performance.
Results. We observed main effects of group ((F(2,80)=7.31, p=.001), condition (F(1,80)=128.02, p<.001), block (F(3,185)=26.49, p<.001), and a condition by block interaction (F(3,240)=3.09, p=.04). Bonferroni post-hoc (p<0.05) showed that middle-aged and older people performed better than young ones, and that there is a decrease in performance with time-on-task, especially in the most demanding (HCL) condition.
Conclusions. The results indicate larger fatigue effects on accuracy performance in younger, especially as the difficulty of the task increased. Further analyses are needed to determine if the better resistance to fatigue from middle-age observed is due to a differential speed/accuracy trade-off between groups, different baseline fatigue levels or the influence of other variables (motivation, cognitive reserve, anxiodepressive level,…).
