Former astronaut Michael Lopez-Alegria, who holds the American record for longest space mission, said he could relate to the study findings. During his 215 days in orbit on the space station, he sometimes had trouble getting back to sleep because he didn't have a sense of lying down or having his head on a pillow.
The lack of sleep and lots of work caused him to sometimes nod off during the day, and the lack of gravity meant that when he fell asleep accidentally he would float away and awaken elsewhere in the station, he said.
"It happened more than once, but I never thought it was a big deal. I thought it was amusing in a way," Lopez-Alegria said in an interview.
Excerpts from astronaut diaries in a NASA report show prevalent sleep problems, with space station residents talking about nodding off while typing and obsessing over getting too much or too little sleep.
"I just need sleep," one unidentified astronaut wrote.
"The morning started disastrously. I slept through two (wake-up) alarms. . . . My body apparently went on strike for better working conditions," wrote another.
Jerry Linenger, a medical doctor and NASA astronaut who spent more than four months on the Russian space station Mir in 1997, said he watched cosmonauts fall asleep in mid-conversation. And after a couple months, Linenger started having sleep problems despite his best efforts, which included using eye shades and bungee cords to put pressure on his body.
"It's kind of like you're wiped out after New Year's Eve, kind of like a hangover or something," Linenger said. "You are aware you're not performing. So I'd be extra careful if I had to switch some buttons."
Later in 1997, a cosmonaut on Mir who had a sleepless night accidentally disconnected a system that gathered solar power for the aging station, said Charles Czeisler, a sleep professor and space researcher at Harvard Medical School.
Czeisler, who wasn't part of the Dinges study, said the new work was important in demonstrating the challenges of a Mars mission.
Astronauts do use sleeping pills to help them sleep.
And one solution experts like Dinges and Czeisler agree on is lighting. Blue evening light is essential for resetting a body's natural rhythms, Czeisler said, and changing the color and timing of lighting has been shown to help people sleep on Earth.