The bacteria living in your guts and mouths could be controlling how you sleep at night. Now scientists want to use them to help you rest better.

As you lie in bed tonight, your body will be a teeming mass of activity. Across almost every inch of your body – and inside it too – billions of tiny organisms are writhing and jostling for space. But if that horrifying thought is likely to keep you up at night, consider this: they might also help you get a better night's sleep.

Emerging research suggests that the communities of bacteria, viruses and fungi that make up our body's microbiota can influence our sleep. Depending on the composition of our personal microbial ecosystem, the amount of shut eye we get can either improve or deteriorate.

And tantalisingly, it could offer new ways of tackling sleep-related conditions caused by a disrupted body clock, described by sleep scientists as circadian rhythms. While many people currently rely on sleeping pills to quell persistent insomnia, the future might see friendly bacteria deployed to help us nod off, and even address obstructive sleep apnoea, a condition in which people struggle to breathe normally while asleep. It would bring new meaning to the term "sleep hygiene".

"The predominant theory for a long time has been that having sleep disorders is disruptive to our microbiomes," says Jennifer Martin, a University of California Los Angeles professor and board member of the American Academy of Sleep Medicine. "But some of the evidence we're seeing now indicates that it's probably a relationship that goes in both directions."

In May, new research presented at an academic conference for sleep scientists summed up what a growing number of other studies are revealing. It found that teenagers and young adults with a greater diversity of microbes in their mouths tended to have a longer sleep duration.

Research has also shown that people with medically diagnosed insomnia have lower bacterial diversity in their guts compared to normal sleepers, something typically linked to a less healthy immune system and impairments in dealing with fats and sugars, which can lead to an increased risk of diabetes, obesity and heart disease. Another study, in which 40 people volunteered to wear sleep trackers for a month and have their gut microbiome analysed, also found that poor sleep quality correlated with a less diverse population of gut microbes.

Plus, people with social jetlag – where their sleep patterns during the working week and weekend vary enormously – had significantly different gut microbiomes to those whose sleep patterns did not vary much, according to data analysed by UK health-tech company Zoe.

"Circadian rhythm disruption occurs in people who stay up later and sleep in on the weekends, those who work long hours, like first responders, police and security, paramedics and the military, and in people who eat too close to bedtime," says Kenneth Wright, a professor of integrative physiology at the University of Colorado Boulder in the US. "This can cause gastrointestinal disturbances and metabolic diseases, which are common for example in shift workers, and a disturbed microbiome may play a role."

It's possible that individuals with disrupted sleep tend to follow less healthy diets, which then impacts their microbiome, suggests Sarah Berry, a nutritional sciences professor at King's College London and chief scientist at Zoe. She cites other research not conducted by Zoe that found that short sleepers tend to subconsciously increase their sugar intake.

"Part of the theory behind this is that when you've had a bad night's sleep, the reward centres in your brain are heightened the next day, and so you seek out that quick fix," she says. "Your brain is kind of tricking you into feeling, 'Ok, I need refined carbohydrates', to get........

© BBC