Limitations Of Caffeine In Combat: Reevaluating Its Efficacy To Mitigate The Effects Of Sleep Deprivation

PURPOSE: This study explored the effects of sleep deprivation and ad libitum caffeine consumption on cognitive performance, risk-taking behavior, and mood states among Israeli Special Forces soldiers during a 96-hour combat exercise. METHODS: Twenty-eight male cadets (age 20.57 ± 0.92 years) from a single unit volunteered for this study. Sleep and activity were tracked via continuous actigraphy. Cognitive performance was assessed using the Psychomotor Vigilance Task (PVT), measuring reaction time and alertness. The Evaluation of Risks Scale (EVAR) measured risk-taking propensity, the Profile of Mood States (POMS) measured mood states and the Karolinska Sleepiness Scale (KSS) measured subjective sleepiness. Measures were collected at 0, 50, and 96 hours. RESULTS: Participants covered 108.5 ± 0.52 km and slept for 12.7 ± 0.5 hours, characterized by multiple short epochs in the initial half and a single, consolidated 5.2-hour period during the second half of the exercise. There were no significant changes in PVT measures during the exercise. However, an increase in risk-taking, especially in the Danger-Seeking factor, was observed at 50 hours (p < 0.015). Mood states, including Anger, Depression, Confusion, Vigor, and Tension, worsened at 50 hours (p < 0.001) but improved at 96 hours. Subjective sleepiness significantly increased at 50 hours (p < 0.001). Ad libitum caffeine consumption did not consistently improve cognitive performance, risk-taking tendencies, or mood state measures. CONCLUSIONS: The study emphasizes that during a combat exercise, under conditions of sleep deprivation, ad libitum caffeine consumption did not reliably mitigate the detrimental effects on cognitive performance, risk behavior, and mood. Despite a common reliance on caffeine among soldiers to maintain alertness and performance, its effectiveness in mitigating the diverse effects of severe sleep loss was limited. This insight is vital for military operations, where reliance on caffeine is often a substitute for sleep. These findings are critical for informing evidence-based caffeine consumption guidelines in military settings, emphasizing the need for a balanced approach that does not rely solely on caffeine to mitigate the impact of sleep loss.