Snoring triggers dementia, according to new research. It cuts off blood and oxygen to the brain-destroying neurons, say scientists. Obstructive sleep apnoea (OSA) affects about 1.5 million Britons - most of whom are undiagnosed.
The walls of the throat relax and narrow - interrupting normal breathing several times a night. Lead author Dr Ivana Rosenzweig, who heads the Sleep and Brain Plasticity Centre at King's College London, said: "We show poorer executive functioning and visuospatial memory and deficits in vigilance, sustained attention and psychomotor and impulse control in men with OSA.
"Most of these deficits had previously been ascribed to co-morbidities. We also demonstrated for the first time that OSA can cause significant deficits in social cognition."
The findings are based on 27 otherwise healthy 35 to 70-year-old men who visited the clinic with a new diagnosis of mild to severe OSA. Such patients are relatively rare as most will also have conditions like obesity, cardiovascular and metabolic disease, stroke, diabetes, chronic systemic inflammation or depression.
Those with severe OSA had worse vigilance, executive functioning, short-term visual memory and social and emotion recognition. This was compared to a group of controls without the sleep disorder who were matched by age, BMI (body mass index) and education.
It shows OSA is sufficient to cause loss of brainpower - which has previously been attributed to high blood pressure, cardiovascular and metabolic diseases and type 2 diabetes. The phenomenon could be due to intermittent low oxygen and high carbon dioxide in the blood, changes in blood flow to the brain, sleep fragmentation and neuroinflammation in OSA patients.
Dr Rosenzweig said: "This complex interplay is still poorly understood but it's likely that these lead to widespread neuro-anatomical and structural changes in the brain and associated functional cognitive and emotional deficits." OSA is highly debilitating for patients and their partners - and potentially dangerous. Symptoms include loud snoring, restless sleep, daytime napping and prolonged morning headaches.
It may occur in up to 30 percent of men and 15 percent of women - around one billion adults worldwide. About eight-in-ten sufferers don’t know they have it. Major risk factors include middle or old age, being obese, smoking, chronic nasal blockage, high blood pressure and being male.
Now Dr Rosenzweig's team, working with colleagues in Germany and Australia, have shown for the first time it can cause early cognitive decline in middle-aged men. Participants were not current smokers or alcohol abusers and had a BMI below 30.
The OSA diagnosis was confirmed by respiratory function tests during sleep at home and in the King's College lab. They wore EEG (electroencephalography) skull caps which measure brain waves while blood oxygen levels, heart rate, breathing and eye and leg movements were also tracked.
Whether co-morbities have similar negative effects on cognition above and beyond those caused directly by OSA is not yet clear. Dr Rosenzweig said: "Our study is a proof of concept. However, our findings suggest that co-morbidities likely worsen and perpetuate any cognitive deficits caused directly by OSA itself.
"What remains to be clarified in future studies is whether co-morbidities have an additive or synergistic effect on the latter deficits and whether there is a difference in brain circuitry in OSA patients with or without co-morbidities."
Overweight individuals are particularly prone to OSA. Preventative measures include shedding the pounds or wearing a mask in bed which blows air into the back of the throat. The condition blights the lives of up to one-in-eight people. Diabetics, smokers and drinkers are particularly prone.
Twice more common in men than women it can begin at any time - including childhood. Dementia blights the lives of more than 920,000 people in the UK - a figure that will rise to 2 million by 2050. Cases worldwide will triple to over 150 million.
With no cure in sight there is an increasing focus of protective lifestyles such as eating the right foods and getting enough exercise - and sleep. The study is in the journal Frontiers in Sleep.
