Caffeine Consumption Aboard the International Space Station and its Relationship to Sleep and Cognitive Performance

Caffeine is a widely consumed performance-enhancing stimulant on Earth that also affects sleep outcomes. Though historically available on spaceflight missions, caffeine use and its influence on sleep and human performance in microgravity have yet to be evaluated. We combined archival data on caffeine use, sleep, and cognitive performance aboard the International Space Station to determine astronauts’ consumption patterns and to characterize the relationships between caffeine consumption, sleep, and cognitive performance during spaceflight. All crewmembers with available data consumed caffeine (mean of 105 mg per day), a value lower than daily use in the regular population, and there were small but significant effects of caffeine on that night's sleep as well as of sleep on caffeine consumed the following day. Caffeine consumption also led to faster reaction times on cognitively demanding tasks. Though the data are limited, they provide important information about crew consumption habits which will be of use in future mission planning.