A new study has shown that obstructive sleep apnoea (OSA) can impact cognition. Photo / Supplied
We all know how mortifying it is when our bed-fellow reveals that we’ve kept them awake all night with raucous snoring.
But for those of us who snore like a freight train, embarrassment is the least of our worries, as new research shows.
If you often wake up feeling breathless or experience excessive sleepiness during the day, you could be suffering from a surprisingly common condition, called obstructive sleep apnoea (OSA), which could leave you at risk of memory issues and, possibly, even dementia.
The new study conducted by researchers at the Sleep and Brain Plasticity Centre at King’s College London has shown for the first time that OSA can impact cognition, even in otherwise healthy individuals. The study found that men aged 35-70 with OSA, and no other health conditions, experienced poorer working memory, along with problems with attention, impulse control, emotion regulation and motor skills.
“It’s a potential public health issue because it’s associated with all sorts of health complications,” says Chris Fox, a professor of clinical psychiatry at the University of Exeter. “We need more diagnoses because there’s an impact on the NHS in terms of illness, but also on the economy. People with OSA won’t be performing as well at their job, and are not as sharp in the morning.”
Cognitive impairment
Fox says it is common knowledge within sleep clinics around the UK that OSA can impact cognitive function. Sleep specialists at the Royal Devon & Exeter Hospital estimate that about 60 per cent of their patients with OSA have some degree of cognitive impairment. OSA is even thought to contribute to car accidents, because sufferers are not able to focus as well as they normally would.
But if left untreated over the course of many years, this cognitive impairment can progress to permanent brain degeneration. OSA has long been known as a significant risk factor for dementia, and according to Guy Leschziner, professor of neurology and sleep medicine at King’s College London and author of The Secret World of Sleep, it can harm your brain both in the short and long term by impacting the body’s ability to cleanse itself of toxins during deep sleep.
“The brain has a waste disposal system called the glymphatic system, which is most active in the deepest stages of sleep,” he says. “It opens up by about 60 percent in deep sleep, but if you disrupt those sleep stages, you interfere with that process of removing these toxic substances from the brain.”
Other wider-ranging impacts
But OSA also has other, more wider-ranging impacts on the brain and the rest of the body. It lowers the amount of oxygen in the bloodstream, causing surges in inflammation, which can put brain cells under stress. Research has also shown that every time an OSA sufferer experiences an obstructive event during their sleep, it causes a rush of adrenaline and activates the autonomic nervous system - the network in the body that regulates vital processes such as heart rate, blood pressure and respiration.
These repeated activations within a short space of time can result in damage to small blood vessels, which not only impact the blood flow to the brain, but can also put the person at a greater risk of stroke, heart failure, hypertension and other forms of cardiovascular disease. The widespread inflammation it causes within the bloodstream may also contribute to an elevated risk of type 2 diabetes.
“To be honest, I think the relationship between cardiovascular disease and OSA is even more important than the impact on cognition,” says Fox. “We need to get more people identified and on treatment to try and manage it, because that could reduce some of the burden on the NHS. If you’re concerned because you’re a loud snorer or you wake up feeling breathless, you should get yourself checked, because the earlier it is detected, the less damage has occurred.”
Causes of OSA
One of the problems is that an estimated 80 percent of people with OSA are completely unaware that they have it. Age is the main risk factor - we are more prone to suffering obstructive events in sleep as we get older because the throat muscles become saggier and less toned – but men are also more at risk because they have larger tonsils. Lifestyle factors are also thought to play a big role, and Fox says that most OSA patients at the Royal Devon & Exeter Hospital tend to be overweight.
Leschziner also points to some genetic factors that can put certain people at a greater risk. “Obesity is a very big risk factor, because the structure of your airway actually changes within the chest itself,” he says. “But we do see sleep apnoea in slim people, and that can come down to the anatomy of your airway. We often see it occurring in families due to the shape of the skull or having a small lower jaw.”
Available treatments
The gold standard treatment for OSA is continuous positive airway pressure (CPAP), essentially a machine that blows air into your nose at night, ensuring that your airway remains open while you sleep. In recent years, scientists have tweaked the technology to make it more comfortable for the user, with newer devices automatically adjusting the pressure in accordance with the patient’s sleep stage or sleeping position.
However, while CPAPs tend to work extremely well in preventing OSA, many patients struggle to use them for more than a few weeks or months. Issues reported range from discomfort, to struggling to get to sleep with a device on their face, complaints from their partner about the noise of the machine, and even abdominal pain from swallowing too much of the pressurised air. Leschziner admits that more than half of patients tend to have quit the devices after one year, unless they experience a particularly dramatic change in their health.
For patients with particularly severe OSA, where the obstructions are happening several hundred times a night, doctors can even recommend surgery to open the top of the palate. The NHS has recently introduced a new procedure called a subcutaneous hypoglossal nerve stimulator for certain OSA patients where the problem is caused by the tongue falling back during sleep and blocking the airway. It is implanted in the mouth through surgery and uses electrical stimulation to cause the tongue to retract during sleep.
“It acts as a kind of pacemaker for the tongue, says Leschziner.”It can cause dramatic improvements, but because it’s very invasive and expensive, it’s likely to only be implemented in highly selected cases.”
Instead, Leschziner recommends that people concerned about OSA initially try less drastic steps. For those where the tongue is contributing to the problem, mandibular advancement devices – which look a bit like boxer’s gum shields – can be fitted in the mouth at nighttime to hold the lower jaw and tongue forward.
Lifestyle changes
But lifestyle changes can also make a big difference. Sedatives such as sleeping pills can make the problem worse because they accentuate the relaxation of the throat muscles during sleep, while drinking alcohol in the evening has a similar effect because it acts as a depressant on the central nervous system.
For people with relatively mild OSA, taking up activities such as singing or breathwork may even make a difference because they help to train and tone the airway. Weight loss can also improve OSA with some studies suggesting that obese individuals who lose 10-15 percent of their body weight can halve the number of obstructive events they experience.
“While weight loss helps, it’s important to be aware that there are other factors involved such as the shape of the airway,” says Leschziner. “Some people will lose small amounts of weight and their sleep apnoea will improve dramatically, and others will lose a very large amount of weight and their sleep apnoea will continue.”
For Fox, it is vitally important that more people are diagnosed earlier with OSA and get treated before too much damage has occurred to their health.
“The potential complications that can arise will be much less if it can be managed,” he says.
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