Sleep – this absurd and amazing habit of losing consciousness for hours – is so universal in the animal kingdom that we generally assume that it is essential for survival. Now, however, scientists who have repeatedly disturbed the sleep of more than a thousand fruit flies have reported that it may be necessary to have less sleep to maintain life, at least in one species.
A handful of studies involving dogs and cockroaches dating back to the end of the 19th century suggest that depriving oneself of sleep can shorten the life span. However, the methods used in some of these studies may make it difficult to say whether the test subjects were harmed by sleep deprivation itself or by the stress of the treatment given to them – for example, being constantly shaken.
The new study took a more moderate approach, hoping to see the true effects of sleep deprivation. The automated system developed by the researchers to monitor the flies monitored their movements using cameras, marking any extended period without movement. When they were not awake several times, men slept about 10 hours a day, women about five hours on average.
To keep the flies awake, the researchers equipped the system with tiny motors that allowed them to flip the flies gently each time they remained motionless for at least 20 seconds. Thanks to this method, the researchers deprived the flies of rest throughout their life, giving them tips hundreds of times a day, so that they could have slept about 2.5 hours a day while sleeping during these days. periods of calm. .
"The results of this experiment were very surprising," said Giorgio Gilestro, a professor at Imperial College London, co-author of the study. published Wednesday in Science Advances.
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While the females participating in the experiment died about ten days earlier than the other flies, the males had a normal life span of about 50 days. Dr. Gilestro suggests that perhaps all that sleep does in terms of essential maintenance can occur in a very very short period of time, so that a minimum of sleep is required to maintain a living organism.
The study has limitations. It was only about a single fruit fly strain, said Dragana Rogulja, a Harvard professor who studies sleep with the help of fruit flies. "In principle, I think it would have been great to test several strains," she said, to understand if other flies, some of which can live much longer, respond in the same way .
In addition, not everyone agrees that scientists were able to accurately record when the flies are awake or asleep. For example, some periods during which flies made small movements were marked as waking hours.
"I'm not convinced that the micro-movements they report are not part of sleep behavior," said Amita Sehgal, a professor at the University of Pennsylvania, a pioneer in the study of sleep at home. the flies. If so, the flies may have slept more than the researchers thought.
Dr. Gilestro replied that these movements are not the same as the contractions that occur when the animals are asleep. Flies wandered between small recorded movements and seemed to feed or groom at those times. "We have looked into this and we think we can exclude that possibility," he said.
The work addresses an interesting question: how much sleep time is related to the beneficial effects of sleep? For most of us, knowing how much sleep you need to stay healthy will probably remain a topic of academic interest. The unpleasant effects of missing even a few hours or being woken up several times during the night tend to discourage the experiences. But it is intriguing to think that perhaps some of this time spent sleeping is less important than the rest.