Abstract
Introduction
Sleep loss has a range of detrimental effects on cognitive ability. However, few studies have examined the impact of sleep restriction on neuropsychological function using an experimental design. The goal of this study was to examine the extent to which maintained insufficient sleep affects cognition in healthy adults compared to habitual adequate sleep.
Methods
This study used a randomized, crossover, outpatient sleep restriction design. Adults who regularly slept at least 7 h/night, verified by 2 weeks of screening with actigraphy, completed 2 phases of 6 weeks each: habitual sleep (>7 h of sleep/night) or sleep restriction (habitual sleep minus 1.5 h) separated by a 6-week washout period. During the sleep restriction phase, participants were asked to delay their bedtime by 1.5 hours/night while maintaining their habitual wake time. Neuropsychological function was evaluated with the NIH Toolbox Cognition Battery at baseline (week 0) and endpoint (week 6) of each intervention phase. The NIH Toolbox evaluates a range of cognitive abilities, including attention, executive functioning, and working memory. General linear models with post hoc paired t-tests were used to assess demographically-adjusted test scores prior to and following each sleep condition.
Results
At the time of analyses, 16 participants were enrolled (age 34.5□14.5 years, 9 women), 10 of whom had completed study procedures. An interaction between sleep condition and testing session revealed that individuals performed worse on List Sorting, a working memory test, after sleep restriction but improved slightly after habitual sleep (p<0.001). While not statistically reliable, the pattern of test results was similar on the other tests of processing speed, executive function, and attention.
Conclusion
In these preliminary results from this randomized experimental study, we demonstrated that sleep restriction has a negative impact while stable habitual adequate sleep has a positive impact on working memory, or the ability to temporarily hold information in mind while executing task demands. This finding contributes to our understanding of the complex interplay between different aspects of sleep quality (i.e., both sleep restriction as well as the maintenance of stable sleep patterns) on cognition and underscores the importance of routine sleep screening as part of medical evaluations.
Support (if any):
Neuropsychological function among workers exposed to aluminum – a mini-review
