Circadian variation in cognition: a comparative study between sleep-disturbed and healthy participants

Aims: To understand the circadian variation in cognition over the course of the day in sleep-disturbed (SD) participants and to compare the findings with healthy controls. Methods: Subjects were screened using Pittsburgh sleep quality index (PSQI), and a total of 24 participants (12 SD and 12 controls) were recruited for the study. P300 was recorded five times a day (8 a.m., 11 a.m., 2 p.m., 5 p.m. and 8 p.m.) for all the participants in both the groups. Results: The results revealed significant variations in P300 wave in both the groups at different time points. The P300 amplitude at 5 p.m. was significantly higher than that at 8 a.m. and 11 a.m., and the lowest peak was recorded at 8 p.m. preceded by that at 2 p.m. for healthy participants. In SD subjects, the highest amplitude was recorded at 8 p.m., followed by 5 p.m., whereas the lowest deflection was recorded at 2 p.m. preceded by 11 a.m. and 8 a.m. Similarly, P300 latency showed the longest value at 8 a.m. followed by 2 p.m., and further followed by 8 p.m. Shortest latency was recorded at 5 p.m. in non-SD participants, whereas SD participants demonstrated a contrasting trend with the longest latency being recorded at 2 p.m., followed by 8 a.m. and 5 p.m. Shortest latency was observed at 8 p.m. preceded by 11 a.m. Conclusion: These results suggest that P300 characteristics vary along the span of the day between SD and non-SD participants.