Sleep continuity and total sleep time are associated with task-switching and preparation in young and older adults

Ageing is associated with changes in sleep and decline executive functions, such as task-switching and task preparation. Given that sleep affects executive function, age-related changes in executive function may be attributable to changes in sleep. The present study used a sleep detection device to examine whether or not wake time after sleep onset and total sleep time moderated age differences in task-switching performance and participants' ability to reduce switch costs when given time to prepare. Participants were cognitively healthy [Mini Mental State Examination > 26] younger (n = 54; mean age = 22.9; 67.8% female) and older (n = 45; mean age 62.8; 71.1% female) adults. Using a task-switching paradigm, which manipulated preparation time, we found that smaller global switch costs were associated with lower wake time after sleep onset and longer total sleep time. Greater preparation effects on local switch costs and adoption of a task-set were associated with lower wake time after sleep onset, although this effect was significant only in older adults when stratified by age group. This association was independent of inhibition and working memory abilities. The lack of interactions between sleep and age group indicated that age differences in switch costs were not moderated by better sleep. Our results suggest that young and older adults may benefit similarly from lower wake time after sleep onset and longer total sleep time in overall performance, and individuals with less wake time after sleep onset are more likely to engage preparatory strategies to reduce switch costs and boost task-switching performance.