Transcranial Direct Current Stimulation (tDCS) Versus Caffeine to Sustain Wakefulness at Night When Dosing at Start-of-Shift

Shift work is necessary in many industries such as healthcare, trucking, defense, and aviation. It is well documented that during the night shift, workers experience the lowest levels of performance and alertness (Czeisler et al. in Science 210:1264–1267, 1980; Akerstedt and Gillberg in Sleep 4:159–169, 1981 [1, 2]). Research has shown caffeine can enhance alertness and performance during overnight work (Muehlbach and Walsh in Sleep 18(1):22–29, 1995 [4]). However, benefits of caffeine decline over time (Miller et al. in Fatigue and its Effect on Performance in Military Environments (Report No. 0704–0188), 2007 [5]). McIntire et al. (Brain Stimul. 7(4):499–507, 2014 [6]) found a promising alternative for use during sleep deprivation called transcranial direct current stimulation (tDCS). tDCS sustained performance throughout the sleep deprivation vigil and for a longer amount of time when compared to caffeine. Three groups of participants received either active tDCS and placebo gum at the start of their shift (1800), caffeine gum with sham tDCS, or sham tDCS with placebo gum. Participants completed 13 sessions of tasks and questionnaires while remaining awake for 36 h. Our results show tDCS could be a possible fatigue countermeasure.