Chronotype and Cognition: Comparison of Executive Functions, Sleepiness, and Fatigue According to Circadian Rhythm Preference

Objective: Individual differences in sleep-wakefulness and, activity timing of individuals are defined as chronotype. This study aimed to compare individuals with different chronotypes in terms of executive functions, sleepiness, fatigue, depression and anxiety. Materials and Methods: A total of 180 people, 116 (64.4%) women and 64 (35.6%) men, aged 18-45 (23.24±7.20) years, were included in the study. Participants were administered a sociodemographic data form, the morningness-eveningness questionnaire (MEQ), Epworth Sleepiness Scale, Fatigue Severity Scale, Beck depression inventory, Beck anxiety inventory, Digit Span test, Stroop test, Verbal Fluency test, Trail Making test (TMT), and Tower of London test. Results: Participants were divided into three groups using MEQ: morning-type (n=48), evening-type (n=42), and intermediate-type (n=90). According to the ANOVA findings conducted with the chronotype groups, there was a significant difference between the groups in terms of sleepiness, fatigue, depression, and anxiety scores, and there was a significant difference in favor of the evening-type only in the TMT-A time variable of the neuropsychological tests. According to the results of the correlation analysis, negative significant relationships were found between the scores from the MEQ, sleepiness, fatigue, depression, VFT-animals, and VFT-KAS. Therefore, it can be said that circadian typology has a limited effect on executive functions. Conclusion: Chronotypes have been found to perform similarly in executive functions such as attention, working memory, verbal fluency, mental flexibility, resistance to interference, planning, and problem-solving.