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Diurnal variation in variables related to cognitive performance: A systematic review

Research output: Contribution to Journal/MagazineReview articlepeer-review

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  • Madhavi Munnilari
  • Tulasiram Bommasamudram
  • Easow Judy
  • David Tod
  • Evdokia Varamenti
  • Ben Edwards
  • Aishwarya Ravindrakumar
  • Chloe Gallagher
  • Samuel Pullinger
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<mark>Journal publication date</mark>1/03/2024
<mark>Journal</mark>Sleep and Breathing
Issue number1
Volume28
Number of pages16
Pages (from-to)495-510
Publication StatusPublished
Early online date17/08/23
<mark>Original language</mark>English

Abstract

Purpose
The aim of this review was to assess current evidence regarding changes in cognitive function according to time-of-day (TOD) and assess the key components of research design related to manuscripts of chronobiological nature.

Methods
An English-language literature search revealed 523 articles through primary database searches, and 1868 via organization searches/citation searching. The inclusion criteria were met by eleven articles which were included in the review. The inclusion criteria set were healthy adult males, a minimum of two timepoints including morning and evening, cognitive measures of performance, and peer-reviewed academic paper.

Results
It was established that cognitive performance varies with TOD and the degree of difference is highly dependent on the type of cognitive task with differences ranging from 9.0 to 34.2% for reaction time, 7.3% for alertness, and 7.8 to 40.3% for attention. The type of cognitive function was a determining factor as to whether the performance was better in the morning, evening, or afternoon.

Conclusion
Although some studies did not establish TOD differences, reaction time and levels of accuracy were highest in the evening. This implies that cognitive processes are complex, and existing research is contradictory. Some studies or cognitive variables did not show any measurable TOD effects, which may be due to differences in methodology, subjects involved, testing protocols, and confounding factors. No studies met all requirements related to chronobiological research, highlighting the issues around methodology. Therefore, future research must use a rigorous, approach, minimizing confounding factors that are specific to examinations of TOD.