Investigations into the influence of sleep, tiredness, time of day, and caffeine on cognitive testing

Cognitive assessment is widely used to evaluate one’s cognitive capabilities. However, subtle external factors may affect the accuracy of test results, if not controlled for, at the time of testing. This thesis investigated the effects of a range of sleep variables, caffeine intake, prior to cognitive testing and current subjective tiredness ratings on several cognitive tests in cognitively-healthy adults. For each study, articipants completed a sleep, tiredness, and caffeine questionnaire and undertook cognitive testing online. Findings revealed that participants reporting a smaller time difference between their subjective preferred time of day (ToD) and the actual ToD of taking part in the cognitive tests performed significantly better on tasks of working memory and false memory, whilst high subjective tiredness and poor sleep quality reduced associative memory performance. Caffeine helped improve performance on a false memory task the further away from one’s preferred ToD of testing the participant was performing. Further investigations extended this using a within-groups repeated measures design and revealed that compared to taking part at one’s chosen nonoptimal ToD, participating in cognitive tasks at one’s chosen optimal ToD significantly improves performance on a range of memory domains. Datasets were combined to establish a novel algorithm based on the finding that age, sleep quality, and the time difference between taking part at one’s subjective preferred ToD and the actual ToD of taking part best predicted cognitive performance. The findings have important implications for clinical, research, legal, educational, sports, and occupational sectors where these variables could be impacting cognitive performance.

URI

https://bradscholars.brad.ac.uk/handle/10454/20935

Type

Thesis

Qualification name

PhD