How long you sleep and how well you sleep are important to your mood, how well you concentrate and how much energy you have, as well as how healthy your body is; chronic sleep deprivation can lead not only to irritability but also to attention deficit and an increased risk of cardiovascular disease, diabetes, hypertension, and obesity [source: American Academy of Sleep Medicine].
Despite pre-mission training and preparation living on board a space station can be disorienting for the body. To avoid any distracting light and heat from the sun, for example, astronauts will cover up any windows they may be near. Astronauts can also choose to wear black sleep masks, the same kind that some people wear on Earth when they want to shut out distracting light. On top of excessive light, strange noises are a big part of the ISS. Because fans, air filters and other noisy equipment provide life support to the astronauts, the ISS is often filled with constant whirring noises -- a constant hum. Astronauts sometimes sleep with earplugs to dampen the sound, but after a while many report they simply get used to it.
Combine the light and the noise with the unnatural feeling of floating, motion sickness, aches and pains, poor ventilation and temperature control, as well as a new sunrise every 90 minutes (the amount of time it takes the space station to circumnavigate the Earth) insomnia and sleep deprivation are a common and serious problem for humans in space; NASA reports that sleeping pills are the second most common drug astronauts take (painkillers are the most common). To help combat astronaut insomnia NASA also budgets at least 8 hours of sleep every day, promotes relaxation techniques, and provides sleep hygiene education but despite it all astronauts average between 30 to 60 minutes less sleep each night than they got at home on Earth [source: Worth]. NASA has also invested $11.4 million to update the fluorescent lights in the ISS's U.S. Orbital Segment with bulbs designed to exploit that our bodily clocks are wound by exposure to light [source: Worth].
And yes, in case you were wondering, it is possible to snore in space.