Caffeinated Beverage Consumption Rates and Reported Sleep in a United States Navy Ship

Abstract

Ship crews live and work in an environment characterized by extreme sleep deprivation. In an attempt to maintain alertness, crewmembers frequently consume caffeinated beverages and energy drinks. As part of a broader study, this work assesses the consumption of caffeinated beverages and investigates the association between caffeinated beverage consumption and reported sleep amount. Crewmembers of a U.S. Navy aircraft carrier (N=767; age 18-49 years) completed a survey with questions pertaining to demographics, exercise frequency, average sleep duration, caffeine beverage consumption, the Epworth Sleepiness Scale (ESS), and the Fatigue Severity Scale (FSS). Results show that the sample of active duty personnel slept approximately six hours per night. Most respondents (~90%) reported using at least one type of caffeinated beverage (~55% coffee, ~50% soft drinks, ~35% energy drinks, and ~35% tea). The participants who reported drinking caffeinated drinks had an average weekly caffeine intake of 812±917 mg (MD=540), ranging from 30 to 9210 mg. Crewmembers who consumed more than 1,270 mg of caffeine weekly (equivalent to 180 mg daily) reported sleeping 5.79±1.17 hours, whereas crewmembers that drank less than 1,270 mg of caffeine reported sleeping 6.17±1.07 hours (p<0.001). Overall, our study shows widespread use of caffeine among active duty crewmembers in our sample. Our results suggest that caffeine intake – in the form of coffee, tea, caffeinated soft drinks, or energy drinks – is associated with sleep and may interfere with sleep patterns while working at sea. Future efforts should be directed at exploring causal relationships involved in this phenomenon. Better understanding of causal links will enable appropriate guidance for better sleep hygiene in the maritime operational environment.