Altering meal timing to improve cognitive performance during simulated nightshifts

ABSTRACT

Altering meal timing could improve cognition, alertness, and thus safety during the nightshift. This study investigated the differential impact of consuming a meal, snack, or not eating during the nightshift on cognitive performance (ANZCTR12615001107516). 39 healthy participants (59% male, age mean±SD: 24.5 ± 5.0y) completed a 7-day laboratory study and underwent four simulated nightshifts. Participants were randomly allocated to: Meal at Night (MN; n= 12), Snack at Night (SN; n = 13) or No Eating at Night (NE; n = 14). At 00:30 h, MN consumed a meal and SN consumed a snack (30% and 10% of 24 h energy intake respectively). NE did not eat during the nightshift. Macronutrient intake was constant across conditions. At 20:00 h, 22:30 h, 01:30 h, and 04:00 h, participants completed the 3-min Psychomotor Vigilance Task (PVT-B), 40-min driving simulator, post-drive PVT-B, subjective sleepiness scale, 2-choice Reaction Time task, and Running Memory task. Objective sleep was recorded for each of the day sleeps using Actigraphy and for the third day sleep, Polysomnography was used. Performance was compared between conditions using mixed model analyses. Significant two-way interactions were found. At 04:00 h, SN displayed increased time spent in the safe zone (p < .001; percentage of time spent within 10 km/h of the speed limit and 0.8 m of lane center), and decreases in speed variability (p < .001), lane variability (p < .001), post-drive PVT-B lapses (defined as RT > 355 ms; p < .001), and reaction time on the 2-choice reaction time task (p < .001) and running memory task (p < .001) compared to MN and NE. MN reported greater subjective sleepiness at 04:00 h (p < .001) compared to SN and NE. There was no difference in objective sleep between eating conditions. Eating a large meal during the nightshift impairs cognitive performance and sleepiness above the effects of time of night alone. For improved performance, shiftworkers should opt for a snack at night.

KEYWORDS:

• Shiftwork
• cognitive performance
• meal timing
• driving
• chrono-nutrition

Acknowledgments

The authors would like to acknowledge the work of the research assistants and nursing staff at the Sleep and Chronobiology Laboratory. Particular thanks to research assistants Dr Alex Agostini, Dr Crystal Yates, Dr Maja Pajcin, Dr Emily Watson, Dr Alex Chatburn, Amanda Santamaria, Zach Cross, Matte Hendrickx, and Thomas Kontou; nursing staff Dr Nerylee Watson, Eva Pederson, Lindy Lawson, Jordan Peters, Caroline Giezenaar. Thankyou to Professor Gary Wittert for his assistance with participant screening. Thank you to Dr Maja Pajcin for her assistance with laboratory equipment for biological sample collection and for her assistance with study preparation. Thank you to the placement students and summer scholars who assisted with data collection. Thankyou also to the participants.

Declaration of Interest

The authors report no conflicts of interest.

Additional information

Funding

This research was funded by an NHMRC project grant [APP1099077] and Charlotte Gupta is funded by an Australian Government Research Training Scholarship; National Health and Medical Research Council [APP1099077].