Could the cause of your sleepless nights be down to the make-up of bacteria living in your gut? And could a faecal transplant offer a solution?
A recent study involving almost 400,000 people showed that those with chronic insomnia were more likely to have certain types of bacteria living in their gut.
Now experts say the findings mean measures that alter the make-up of the microbes living in the gut, such as diet tweaks; taking probiotics (friendly bacteria); prebiotics, which act as food for the good bacteria; or even a transplant of faecal matter from someone without sleeping difficulties, should now be trialled as drug-free ways to treat insomnia.
This may also explain why some people experience insomnia, as known triggers – such as stress, lifestyle and hormonal changes around the menopause – don’t apply in around 50 per cent of cases.
‘I’m convinced that the gut has a part to play in insomnia,’ says Dr Sara McNeillis, a consultant in sleep medicine at University College London Hospitals NHS Foundation Trust.
‘Studies like this have shown that not only does bacteria cause insomnia, but that insomnia can change the bacteria in the gut as well.’
Every year around 30 per cent of us experience a period of insomnia, and 10 per cent of the adult population are known to have chronic insomnia, says Professor Guy Leschziner, a consultant neurologist at the Sleep Disorders Centre at Guy’s and St Thomas’ NHS Foundation Trust in London.
Chronic insomnia is defined as being unable to sleep, or feeling that your sleep quality is poor, for more than a few nights a week for three consecutive months.
Chronic insomnia is defined as being unable to sleep, or feeling that your sleep quality is poor, for more than a few nights a week for three consecutive months (picture posed by model)
Conquering insomnia is important as poor sleep is linked to an array of health problems, including heart disease, type 2 diabetes, obesity, mental health problems, a weakened immune system and impaired cognitive function, says Professor Leschziner.
For the latest study, researchers at Nanjing Medical University in China analysed data from 387,000 people with insomnia. As well as finding 14 types of gut bacteria associated with a higher likelihood of insomnia, including Odoribacter (which is generally considered to be beneficial for gut health), they were also able to identify eight groups of bacteria linked with a lower risk of insomnia (which were not present in high levels in this group).
The researchers’ analysis, published in General Psychiatry in August, also found that people with insomnia had reduced levels of seven groups of bacteria that are thought to be important for sleep.
Friendly bacteria, which include strains of Lactobacilli, promote better sleep by producing short-chain fatty acids when they break down fibre (found in wholegrains, vegetables, pulses and nuts) in the gut.
Short-chain fatty acids stimulate the production of the amino acid tryptophan, which is converted into serotonin – a chemical messenger that aids sleep.
But if your sleep is repeatedly disturbed, it leads to the activation of genes that allow pro-inflammatory ‘bad’ bacteria such as E. coli (which can cause gut symptoms including diarrhoea) to thrive, explains Dr McNeillis.
‘However, studies which tried to reset the gut microbiome by using probiotics or prebiotics didn’t show much difference, so more research is needed,’ she says.
It’s unclear to what extent gut bacteria directly cause insomnia or are a consequence of it, adds Professor Russell Foster, director of the Sleep and Circadian Neuroscience Institute at the University of Oxford.
‘Insomnia can cause stress, which then impacts the vagus nerve (which controls bodily functions including digestion, heart rate and the immune system) – and this in turn could change the nature of the gut and therefore the gut bacteria,’ he says.
‘If this is proven then it is possible that probiotics could help.’
A more radical solution suggested by the researchers might be microbial transplantation – known colloquially as a poo transplant – when a stool sample from a healthy donor is transplanted into another patient via a colonoscopy, which involves inserting a thin flexible tube into the colon.
In the meantime, Dr McNeillis recommends that those who have trouble sleeping follow a Mediterranean-style diet, rich in fruit, vegetables, pulses, fish and olive oil – and avoid processed foods and saturated fats.
‘This is essentially an anti-inflammatory diet that promotes growth of the better groups of bacteria,’ she says.
But be mindful of when you eat. Studies in mice have shown that going to bed hungry leads to more waking in the night than going to bed full.
However, Dr McNeillis also recommends not eating your last meal within three hours of bedtime – as leaving it any later may promote obesity, because more of the calories you consume are stored as fat rather than being put to use.
Obesity itself also has an impact on sleep – excess body weight puts a physical strain on the body, especially on the respiratory system, leading to breathing problems, disturbed sleep quality and decreased sleep duration.
And it’s not only gut health now being implicated when it comes to insomnia. Avoiding strenuous exercise in the evening could also help, as it disrupts sleep by making the sympathetic nervous system (which is associated with ‘fight or flight’ responses) more alert, according to a study published in April in the journal Nature Communications.
Dr Sara McNeillis is a consultant in sleep medicine at University College London Hospitals NHS Foundation Trust
Researchers at Monash University in Melbourne, Australia, examined data from 14,689 physically active individuals who wore a movement tracker for a year – and found that exercising within four hours of sleep was associated with delayed sleep onset, shorter sleep duration and reduced sleep quality.
Temperature can also play into this, as our core body temperature needs to lower.
‘The ideal bedroom temperature is between 16c and 20c,’ says Professor Leschziner, as this is the temperature at which you will typically be most comfortable.
Women are often colder in the night than men because men tend to have a higher muscle-to-fat ratio than women, and muscle generates more heat than fat, so using separate duvets with different togs if you share a bed can be useful, adds Professor Foster.
Women commonly suffer from insomnia around the time of the perimenopause and menopause, due to a fall in the level of oestrogen, which promotes sleep.
‘Oestrogen receptors in the brain help to regulate our circadian rhythm [our natural body clock] so you tend to get fragile sleep and wake in the night during the menopause,’ says Dr David Garley, a GP based in Bristol and director of the Better Sleep Clinic.
One measure known to help tackle insomnia is getting exposure to natural daylight, explains Professor Foster.
‘It’s important to get enough outside light in the day so that your body clock knows that it’s daytime and does not become too sensitive to light later in the evening.’
This can shift your body clock and make it difficult to wake up when you need to in the morning, he says.
But if you’re outside for less than 30 minutes then ditch your sunglasses, as wearing them could counteract your light exposure, adds Professor Foster.
Contrary to popular belief, looking at a phone or tablet before bed won’t have much impact on sleep, as long as you’re getting enough daytime outdoor light, he adds. But make sure that what you’re looking at doesn’t cause stress or distress.
‘The screens emit a very dim light, which won’t have an impact – unless you’re looking at them for several hours,’ he says.
Sleeping tablets or over-the-counter herbal sleep aids can be useful for a couple of weeks ‘if you’re going through a stressful period’, adds Professor Leschziner, but he says long-term use ‘is fraught with difficulties – side effects, loss of efficacy and dependency’.
Another measure that can help you sleep is getting up if you can’t drop off. Professor Leschziner advises: ‘If you can’t sleep after 20 minutes, get up and do something calming, such as listening to relaxing music or reading a book in a different room with low-level lighting – and then try again when you feel sleepy.’
