Effort During Prolonged Wakefulness Is Associated With Performance to Attentional and Executive Tasks but Not With Cortical Excitability in Late-Middle-Aged Healthy Individuals

Objective: Sleep loss negatively affects brain function with repercussion not only on objective measures of performance but also on many subjective dimensions, including effort perceived for the completion of cognitive processes. This may be particularly important in aging, which is accompanied by important changes in sleep and wakefulness regulation. We aimed to determine whether subjectively perceived effort covaried with cognitive performance in healthy late-middle-aged individuals. Method: We assessed effort and performance to cognitive tasks in 99 healthy adults (66 women; 50-70 years) during a 20-hr wake extension protocol, following 7 days of regular sleep and wake times and a baseline night of sleep in the laboratory. We further explored links with cortical excitability using transcranial magnetic stimulation coupled to electroencephalography. Results: Perceived effort increased during wake extension and was highly correlated to subjective metrics of sleepiness, fatigue, and motivation, but not to variations in cortical excitability. Moreover, effort increase was associated with decreased performance to some cognitive tasks (psychomotor vigilance and two-back working memory task). Importantly, effort variations during wakefulness extension decreased from age 50 to 70 years, while more effort is associated with worse performance in older individuals. Conclusion: In healthy late-middle-aged individuals, more effort is perceived to perform cognitive tasks, but it is not sufficient to overcome the performance decline brought by lack of sleep. Entry in the seventh decade may stand as a turning point in the daily variations of perceived effort and its link with cognition.

Automated summary

This study aimed to investigate whether subjectively perceived effort covaried with cognitive performance in healthy late-middle-aged individuals. Results showed that perceived effort increased during wake extension and was highly correlated with subjective metrics of sleepiness, fatigue, and motivation, but not with variations in cortical excitability. Moreover, increasing effort was associated with decreased performance in certain cognitive tasks. Importantly, the variations in perceived effort during wakefulness extension decreased from age 50 to 70 years, and more effort was associated with worse performance in older individuals.