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Is this why we get tired? Brain cells that govern bedtime get more active the longer sleep is delayed

Sleepy feeling might be caused by type of brain cell becoming more active
Researchers from Johns Hopkins University say they've identified certain neurons which are responsible for sleepiness
This could offer us insights into human sleep disorders such as insomnia

Published: 08:13 GMT, 24 May 2016 | Updated: 08:26 GMT, 24 May 2016

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We have all experienced that sleepy feeling after a long day in the office, but perhaps do not usually think about what is actually making us experience this mental fatigue.

But now researchers claim to have identified key brain cells that make us feel sleepy - and they get more active the longer you put off your bedtime.

The study found a group of brain cells in charge of the so-called 'sleep drive' becomes more active the longer animals are kept awake.

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The results of the study could offer us insights into human sleep disorders such as insomnia, and open up new strategies to promote long-lasting sleep for those who don't find solace with current therapies

The research, which was conducted by scientists at Johns Hopkins Medicine, Baltimore, Maryland, looked at the brains of fruit flies, which they say behave in a similar way to humans when asleep.

They were able to identified certain cells in the brain that are responsible for creating the feeling of chronic sleepiness when bedtime is delayed.

They also found the same brain activity can actually help the flies to remain asleep when they do drop off.

When the neurons were switched off, flies who had been deprived of sleep got about 66 per cent less 'rebound sleep' compared to flies who had been following their normal sleep cycle, suggesting that they felt less sleepy

Dr Mark Wu, associate professor of neurology at Johns Hopkins Medicine, said: 'With what we believe is the first identification of a mechanism behind the adjustable nature of sleep drive, researchers can look for the same processes in mammals, including, one day, in humans.'

IS IT WORTH HITTING SNOOZE?

To many, the snooze button can feel like a welcome relief, but it might be better to set an alarm later and get up right away.

This is because sleep goes in cycles, beginning with a couple of minutes dozing, 10 to 20 minutes of light sleep, and then slipping into a longer period of deeper sleep.

The cycle starts every 90 minutes and as the night goes on, light sleep turns to dreaming.

It might feel good to put the alarm on snooze, but at that point the cycle has already been broken and the light bursts of sleep feel unsatisfactory and make getting up harder.

The study used over 500 strains of fruit fly, and found that 'R2 neurons' - specialised cells which transmit nerve impulses - were responsible for making the flies sleepy.

When these neurons were switched off, flies who had been deprived of sleep got about 66 per cent less 'rebound sleep' compared to flies who had been following their normal sleep cycle, suggesting that they felt less sleepy.

This shows that the more of these specialised brain cell are active, the sleepier you are likely to feel.

Dr Wu added 'Figuring out how sleep drive works should help us one day figure out how to treat people who have an overactive sleep drive that causes them to be sleepy all the time and resistant to current therapies.'