Performance overnight in shiftworkers operating a day-night schedule

Area of Science:

• Human Physiology
• Sleep Science
• Occupational Health

Background:

• Work performance can be affected by circadian rhythms and time of day.
• Overnight work presents unique challenges to cognitive function and vigilance.
• Caffeine is a widely used stimulant with potential performance-enhancing effects.

Purpose of the Study:

• To assess the impact of a day-night work schedule on performance.
• To investigate the effects of 300 mg caffeine on overnight performance.
• To examine the relationship between performance, circadian rhythmicity, and caffeine use.

Main Methods:

• Performance tests were conducted during daytime (0800-1700) and overnight (1700-0800) work periods.
• Sleep electroencephalogram, oral temperature, and urinary electrolyte excretion were monitored.
• The effects of 300 mg caffeine were evaluated during overnight work shifts.

Main Results:

• Daytime performance impairment was minimal, affecting only continuous performance tests.
• Overnight performance impairment was more significant, notably including reduced vigilance.
• Impaired overnight performance correlated with time on task and circadian rhythmicity.
• Caffeine administration partially alleviated overnight performance deficits.

Conclusions:

• Overnight work significantly impairs performance, particularly vigilance, compared to daytime work.
• Circadian factors and prolonged work duration contribute to performance decrements during night shifts.
• Caffeine (300 mg) offers a partial countermeasure to the negative effects of overnight work on performance.