Abstract
For occupations that demand 24-hour capability (e.g., the emergency services or military), there is a need for effective and practical countermeasures for fatigue. The research presented in this thesis investigated novel uses of caffeine and light to reduce fatigue and enhance performance, without compromising sleep, that are feasible for use within an occupational environment.
It was found that caffeine gum presents an easy to administer, low-cost, and readily available countermeasure that could feasibly be used within several occupational environments. One-hundred and 200 mg doses administered upon abrupt waking from nocturnal sleep served to improve subjective alertness, fatigue and mood over a two-hour waking period in a dose dependent fashion, although 200 mg was found to impair subsequent sleep. The most appropriate dose for use within an occupational environment would therefore need to be carefully considered. A partial withdrawal from caffeine in high habitual consumers could potentially optimise the benefits afforded by lower caffeine doses.
Light interventions delivered during breaks within a working shift is a practical countermeasure that would not compromise work task performance, although consideration needs to be given to the impact on visual comfort when moving between different light environments. The delivery of a dynamic light intervention within the breaks of a simulated night shift was feasible and acceptable to implement, and had positive effects on alertness, fatigue, and performance, with little impact on subsequent sleep. A five-minute gradual modulation of spectral content and illuminance appears to be the optimum transition between light environments to preserve visual comfort.
The results of the research presented in this thesis demonstrates the potential benefits of using caffeine and light as a fatigue countermeasure separately. With the development of faster-onset caffeine formulations and more efficient lighting technology, the combined use of caffeine and light as a fatigue countermeasure should be further investigated.