Astronauts suffer considerable sleep deficiency in the weeks leading up to and during spaceflight, according to the most extensive study of sleep during spaceflight ever conducted, published in The Lancet Neurology journal.
Fatigue and sleep deficiency are common complaints among astronauts, but this is the most comprehensive study to include both objective evaluation of sleep (via an actigraph, a device worn on the wrist which records sleep and wake cycles) and subjective evaluations (via a daily diary recording alertness and sleep quality).