Impact Of A 20-hour Rotating Watch Schedule On Cognitive Performance And Risk-taking Behavior In Israeli Navy Submariners

PURPOSE: To assess the effects of a 20-hour rotating watch schedule on cognitive performance and risk-taking behavior in Israeli Navy submariners. The non-circadian-aligned schedule, characterized by a continuous shift rotation, was hypothesized to impair alertness and increase risk-taking propensity. METHODS: Twenty male submariners (21.6 ± 4.3 yrs) participated in a five-day at-sea mission. Shifts were divided into seven-watch segments over the 20-hour cycle. Cognitive alertness was assessed using the Psychomotor Vigilance Task (PVT) and risk-taking behavior was evaluated using the Evaluation of Risks (EVAR) scale. Actigraphy provided objective sleep metrics, and caffeine intake was monitored to account for its influence. RESULTS: Submariners exhibited fragmented sleep, averaging 8.3 ± 0.2 hours per day across multiple 3.7 ± 0.8 hour sleep epochs. Alertness, as measured by premature PVT responses, declined significantly during the late afternoon watch VI (17:00-20:00) and night watch VII (20:00-00:00) (p = 0.014). Risk-taking propensity increased significantly during watch IV (11:00-14:00) and watch V (14:00-17:00) (p = 0.050). Caffeine consumption was significantly reduced at sea compared to land (p = 0.027), suggesting its strategic use by submariners to regulate alertness. CONCLUSIONS: The 20-hour rotating schedule disrupts sleep architecture, impairs cognitive alertness in the evening and elevates risk-taking behavior in the afternoon. These results underscore the need for circadian-aligned scheduling and evidence-based caffeine guidelines to enhance operational performance and well-being among submariners. Disclaimer: Views expressed are not official US Army, DoD, or government policy.