Going without sleep for too long kills animals but scientists haven’t known why. Newly published work suggests that the answer lies in an unexpected part of the body.
nside a series of tubes in a bright, warm room at Harvard Medical School, hundreds of fruit flies are staying up late. It has been days since any of them have slept: The constant vibrations that shake their homes preclude rest, cling as they might to the caps of the tubes for respite. Not too far away in their own tubes live other sleepless flies, animated with the calm persistence of those consigned to eternal day. A genetic tweak to certain neurons in their brains keeps them awake for as long as they live.
They do not live long. The shaken flies and the engineered flies both die swiftly — in fact, the engineered ones survive only half as long as well-rested controls. After days of sleeplessness, the flies’ numbers tumble, then crash. The tubes empty out. The lights shine on.
We all know that we need sleep to be at our best. But profound sleep loss has more serious and immediate effects: Animals completely deprived of sleep die. Yet scientists have found it oddly hard to say exactly why sleep loss is lethal.
Sleep is primarily seen as a neurological phenomenon, and yet when deprived creatures die, they have a puzzlingly diverse set of failures in the body outside the nervous system. Insufficient sleep in humans and lab animals, if chronic, sets up health problems that surface over time, such as heart disease, high blood pressure, obesity and diabetes. But those conditions are not what slays creatures that are 100% sleep deprived within days or weeks.
What does sleep do that makes it deadly to go without? Could answering that question explain why we need sleep in the first place? Under the pale light of the incubators in Dragana Rogulja’s lab at Harvard Medical School, sleepless flies have been living and dying as she pursues the answers.
On a cold morning this winter, Rogulja leaned over a tablet in her office, her close-cropped dark hair framing a face of elfin intensity, and flicked through figures to explain some of her conclusions. Rogulja is a developmental neuroscientist by training, but she is not convinced that the most fundamental effect of sleep deprivation starts in the brain. “It could come from anywhere,” she said, and it might not look like what most people expect.